Follow the steps:
1. Connect DB Engine (sqlserver)
2. Right click on DATABASES
3. Select Restore Database
4. Select bak file from your Hard-drive
5. & click ok, it will start to execute
6. Depends upon your back up file size it will take time
Hope it works.
Or
try this
http://www.youtube.com/watch?v=BHevcPDAU7Q[
^]