To restore a MSSQL BAK database backup, do the following steps:
1. Open Management Studio and connect to the database server.
2. Right-Click on Databases and select Restore Database...
3. In the dialog that appears, select Device and then click the ... button:
4. In the dialog that appears, select File then click Add
5. In the dialog that appears, browse for your BAK database backup and click OK.
6. Click OK to confirm your backup device selection:
7. Back on the Restore Database screen, give the database a descriptive name.
8. Last, click on Files then select Relocate all files to folder and then click OK.
9. The database will now be restored and visible through Management Studio
If restoring the same database multiple times or if you have two different databases that have had the same name, replace the name of the database in the "Restore As" file name with the name of the new destination database.