1. Stop your server
2. Click files.
3. Click FTP file access
4. Click the login button - so that you see all your files
5. Find the file with your world name.
6. Click the little box next to your world name and then click the Rename Button
7. Type in new world name and hit submit (you must do this step, as the restored backup will not overwrite a world of the same name)
8. Click back to control panel
9. Click backup
10. Click restore
11. Find the zip world you want to restore and click restore.
12. You can see it unpack in the console. Once finished, Start your server