How do I make a file private?

To make a file private from public access you will need to click on the Link option, which will appear under the Task menu on the left when you highlight a file. A popup box will appear where you can select Make Private. The file will now be made private and no users will be able to search for it in the community 

If a file has been shared with a friend which you now want to make private then you need to click on Send. This option will also appear on the left under the Task menu when you highlight a file. A popup box will appear and you will be able to see who you have shared the file with and can revoke their access to the file.