If you have made a backup via the Service > Backups page, you can restore it by:
1) Visit any Console submenu for the game software you intend to restore, ensure the server is shut down by clicking the red stop button on the right side of the page and waiting for the running indicator on the games menu to turn red.
*If the server is running, some files may not be overwritten OR may be overwritten by data in RAM when the server reboots, reverting your restoration changes.
2) Click Restore next to the backup you want to restore on the Service > Backups page.
Restoration may take a few mins depending on the size of your backup, the more data, the longer it will take.