If the database schema you’re restoring already exists, you must first delete it. Open pgAdmin by navigating to: Start -> Programs ->PostgresSQL--> pgAdmin.
You may choose to use the command line tool pg_restore.exe to restore the database. To restore a backup, execute the following command:
pg_restore --dbname=cm --format=custom -U postgres -W C:\tmp\db.backup
Please refer to the PostgreSQL manual for more details on the command line tools.