Don't create an empty database and restore the .bak file on to it.
Use 'Restore Database' option accessible by right clicking the "Databases" branch of the SQL Server Management Studio and provide the database name while
providing the source to restore.
Also change the file names at "Files" if the other database still exists. Otherwise you get "The file '...' cannot be overwritten. It is being used by database 'yourFirstDb'".