Alternately, you can drag an individual document, spreadsheet or presentation from the Docs list into the folder of your choice, located in the Docs list page sidebar.
Once either of these steps is taken, your document, spreadsheet or presentation will show up in the folder you selected. Note, also, that it's possible to assign a single document, spreadsheet or presentation to multiple folders.You can see all your docs, regardless of the folder you put them in, by clicking on All items.