you can run this command without creating new database

RESTORE DATABASE testdb

FROM DISK=' 'c:\sqlbackups\testdb.bak'

WITH MOVE 'testdb_Data'

TO 'C:\Program Files\Microsoft SQL Server\MSSQL.1\MSSQL\Data\testdb.mdf',

MOVE 'testdb_Log '

TO 'C:\Program Files\Microsoft SQL Server\MSSQL.1\MSSQL\Data\testdb_log.ldf'