If you don’t have some kind of version control software (Perforce, Subversion, Git, etc.) then the quickest way to make a backup is go to the menu bar at the top of the editor and select File > Package Project > Zip Up Project. This will generate a ZIP archive of your project, minus things like temporary files and derived data that you don’t really need for backup purposes.
To restore it, simply unpack the ZIP into a folder and double-click the project file.