If you have the Database Backup File then you can easily restore it to your SQL Server. I will use SQL Server Management Studio (SSMS) to restore the database.
In the SQL Server Management Studio (SSMS) right click the Database node and select Restore Database. This will open the Restore Database window.
In the Restore Database window select DeviceSource option and click the … button.
This opens Select backup devices window.
In the Select backup devices window click the Add button. This opens Locate Backup File window.
In the Locate Backup File select the backup file of your database and click the OK button.
You will see the Select backup devices window now contains the location of the database backup file. So click the OK button on the Select backup devices window too.
You will see the Restore Database window is now ready to restore the database. Click the Options link on the top left corner.
Here in the Restore options check the option that says Overwrite the existing database (WITH REPLACE) and finally click the OK button.
Your database will be restored and SSMS will show the success message.