Can't restore sql bak file to a new database
Close all tabs on the right side in the management studio and try again.  It is possible that you clicked on the database and some tab on the right side is accessing it.

Alternatively, you may use this sql (replace file name and path)

USE master;
GO
ALTER DATABASE DELVIPROD_JUNE SET SINGLE_USER WITH ROLLBACK IMMEDIATE;
restore database DELVIPROD_JUNE FROM DISK = 'C:\temp\db.bak'   WITH replace 
ALTER DATABASE DELVIPROD_JUNE SET MULTI_USER;


If you want to make a copy of a database, this might help https://serverfault.com/questions/62590/how-to-duplicate-mssql-database-on-the-same-or-another-server