Restoring SQL server database ".bak" file

Right click on the database tab –> All Tasks –> Restore Database –> From device –> Select Devices –> Add your .bak file. Click OK. 

Now click the options tab. Here you will see the logical file name of your database. At its right side there will be a physical path of this file. Make sure this path is redirecting to the location where your database files exist, normally default location is "C:\Program Files\Microsoft SQL Server\MSSQL\Data" at the end of this path concatenate your file name. After concatenation your path should be something like this

C:\Program Files\Microsoft SQL Server\MSSQL\Data\test.mdf

C:\Program Files\Microsoft SQL Server\MSSQL\Data\test_Log.ldf.

Now click ok. Large databse normally takes lot of time.