The TL;DR Version

The quick and easy way to use KerbCam basic path recording and playback features:

Press F8 to open KerbCam.
Press “Create simple path” to create a new path.
Move the camera to desired starting camera position (right mouse button drag, middle drag to pan, mouse wheel to zoom, etc - usual KSP controls). Press “New key” button.
Move camera to next camera position, press “New key” button.
Repeat step 4 until you’ve created the path. Toggle “Draw” to visualize the path around your vessel.
Press F2 to hide the KSP GUI, and press the “Insert” key on the keyboard to start playback of the path, using an external video tool to record your beautiful spacecraft as the camera swoops (sort of) majestically around it.
…
Profit!

First Look at the Main Window

By default, pressing F8 will open the KerbCam main window, pressing it again will close it.

First, it is useful to know some terms that KerbCam uses in this context:

“Path” - A path is a recorded set of points and rotations for the camera to move through over time. When “playing” a path, KerbCam will take control of the camera, and move it through the path’s positions and rotations. A path consists of “keys”.
“Key” - A point defined by the user within a path, defining how a camera is to be positioned and oriented at a given time in a path.
“Relative to” - By default, when KerbCam takes control of the camera, the camera will be moved and rotated relative to the currently active vessel in KSP. This means that as the vessel moves and rotates relative to other objects, the camera will follow along with it. Quite often this is exactly what you want, but sometimes it is desirable to track a different vessel instead. More explanation on this in the notes.
“6DoF” - Six degrees of freedom camera controls. These allow you to move a camera in 3 different directions, and rotate on 3 different axes. This is more flexible than the camera view controls built into KSP, and can be used to set up more elaborate fields of view for screenshots or path points that would otherwise be impossible with the inbuilt camera controls of KSP. Note that the 6DoF camera controls are not required to make path points, except where it would be otherwise impossible to place the camera, or if moving the camera relative to a non-active vessel.

Paths can be saved/loaded to disk to persist between KSP sessions with the save/load buttons. The saved paths are saved to a text file called “kerbcam-paths.cfg” within the top-level KSP install directory.

Configuration Window

KerbCam’s configuration primarily allows for binding of controls to keys on the keyboard.

Most keyboard keys should be usable as a binding, and modifiers (such as shift, control, alt) may be used in combination. All KerbCam’s key bindings may be unbound (cleared), except for the window toggle (as there is currently no way to toggle the window other than by keyboard).

Note that KerbCam’s configuration will not be saved unless the “Save” button is pressed in the configuration window.

Camera Controls

Opening out the camera controls displays this panel of buttons. The “Controlling camera” toggle enables and disables KerbCam’s control of the camera. The sliders control how fast the camera is translated and rotated by the array of buttons below them, note that the sliders are on an exponential scale, so dragging them to the far-right will allow for very fast movement for large distances, and to the far-left will allow for very fine-grained control.

Creating and Editing a Path

By pressing the “New simple path” button, a new path is created and selected. Controls for editing and playing back that path become available.

The playback controls do not change the path in any way, but rather allow control/visualization of the path, and are as follows:

“Play” - Enabling this will make KerbCam take control of the camera, and move it along the path. If, however, “Pause” is also selected, the camera will stay still at the current playback time. Disabling this will return control of the camera back to normal.
“Pause” - Enabling this prevents the playback from moving forwards. This can be enabled prior to pressing play, in order that a path can be set up ready to play, then the GUI hidden (by default, F2 toggles the GUI in KSP), prior to unpausing when the sequence is ready to be recorded by an external capture program.
“Draw” - Not a playback control as such, this draws a white line to visualize the path that the camera will move along. It is suggested that this be turned off prior to recording a sequence, as the white line will clip into the camera in an odd way.
Seek control - This consists of:

a number (in seconds) representing what point in the path’s current playback time is.
a slider control, visualizing the playback over time, and also allowing the user to fast-forward/rewind the playback time.
a number (in seconds) stating the length of the path’s playback.

Below the playback controls is the key list. This lists the time of each key, and allows a key to be selected for editing.

Below the key list is a control to create a new “key” within a path. This will create a new key 5 seconds after the last key in the current path, at the position and orientation that the camera is currently at.

The other control is the “Timescale” toggle. This enables key frames to not only control the camera’s position/orientation over time, but also to change how fast game time is flowing. This is intended to help produce slow/fast-motion effects. It is advised not to use this if you intend to be warping time during playback of the path.

Key Editing

When keys have been created for a path, and one of the keys is selected, additional controls become available:

The controls are:

The “@ 8.00s” text box changes the time within the path that the key is. In this example, the selected key will be the position of the camera 8 seconds into playback. A vertical slider just to the left of this (and to the right of the key list) also allows this time to be set within the path by mouse.
The timescale slider changes how fast game time is at this key. This will only be visible if the “Timescale” toggle is enabled for the path. “Reset timescale” resets this to 1x speed.
“Set” - Move the selected key to the current camera position. This is useful if you want to fine-tune the position of the key.
“View” - Move the camera to the view of the key.
“Remove” - Deletes the key from the path.

Notes

Relative-to

When an object is selected as the “relative-to” object, then the camera’s “base” movement will be to move with that object. I.e if the object moves up, the camera will move up by the same amount, keeping the same relative position.

One example of how this may be useful is where you are filming a Kerbal climbing a ladder on the side of a vessel, you may want to keep the camera trained on the capsule, and also avoid the sudden camera movement as the Kerbal transitions from a ladder at one angle, to another at a different angle. By selecting the vessel as the relative-to object, the camera will not move relative to the vessel, whilst you remain in control of the Kerbal.

Note that vessels are only available as the relative-to object within a certain distance of the actively controlled vessel.