Microsoft SQL Server Management Studio is available for free from Microsoft and can be downloaded through this link: https://msdn.microsoft.com/en-us/library/mt238290.aspx
Once downloaded, Install and open MSSQL Management Studio from the Start menu.
Connect to the server, provide the required credentials.
Choose your database name from the list you have created from the Websitepanel control panel. Here it is showing as "test"
Right-Click on the Database name "test" and Click "Tasks". Click "Restore", then click "Database"
Choose "Device", then click "..."
Select the Backup Devices.
Find the Backup database from the folder.
Click on OK.
Restore the Database
Choose "Options" and "Restore Options".
Tick the "Overwrite the existing database 9WITH REPLACE)"
Delete the Database existing user.
Delete the object
How to connect to User mapping