You need to use the WITH RECOVERY option, with your database RESTORE command, to bring your database online as part of the restore process.

This is of course only if you do not intend to restore any transaction log backups, i.e. you only wish to restore a database backup and then be able to access the database.

Your command should look like this,

RESTORE DATABASE MyDatabase
   FROM DISK = ‘MyDatabase.bak‘
   WITH REPLACE,RECOVERY

You may have more sucess using the restore database wizard in SQL Server Management Studio. This way you can select the specific file locations, the overwrite option, and the WITH Recovery option.