First, log into hostControl and select the "Databases" menu item from the General section of the menu.
Find the database you wish to restore to and choose the "Select" button to the left of it.
This will bring up the database's information as well as give you some button options underneath. Select the "Restore" button.
If you are restoring from a backup made within the control panel, this will already be placed within the "App_Data" folder in the root of the domain. Select the domain name from which the backup is placed and then choose the file from the drop down menu. If you are restoring from a database backup from your computer, ensure you upload it the "App_Data" folder in your domain's root. (You may need to create this folder if it is not there already). Confirm the details and then select the "Restore" button.
Depending on the size, it may take a few minutes to complete restoring. Once restored, you will see the below completed notification.