Hello Purushottam,
As I mentioned earlier, you will probably need to backup and restore your DB and start it in Standby Mode, it will not be ready to use as the DB will be in standby mode. However, you can keep shipping the logs over to the DR site to keep your standby DB updated.
In the event of a DB crash on primary, your standby db can be started as primary db and then it would be usable.
Regards,
Siddhesh