1.  Go to the Chrome web store (https://chrome.google.com/webstore/category/apps) and search for Capture, Explain, and Send Screenshots.
2. Click to add it to Chrome.
   

3. To the right of your address bar, click on the extension.  It will look like this:  
4. Select the type of screenshot you want to take.

5. Click and drag to take an area screen shot.  

5.  Annotate on your screenshot.  Select any color and then type, draw arrows, add circles, doodle, etc. to add to your screenshot.  Then click Done.

6.  Select where you want your screenshot to go.