You can upload a backup file to the Plesk's storage, by running the Tools & Settings > Backup Manager > Upload wizard. Before starting the upload, Plesk will prompt you to enter the following backup parameters:
Backup file location.
Note that if you select a file containing an incremental backup, this file includes the preceding full backup and all incremental backups made before the selected incremental backup.
The password you used for protection.
This is the password that you used for protecting the backup data.
Note: If you provide an incorrect password, Plesk will warn you but will upload the backup to the server anyway. During the backup restoration, you will be prompted to enter the password again.
If you want to upload a backup file created on another server or in a Plesk version earlier than 11.5, you should allow uploading such backups by selecting the option Upload backup files without a valid signature. In this case, Plesk will upload the files and display a warning. If you do not select this option, Plesk will display an error message and the files will not be uploaded.