Membership Pro Subdomain content protection

I have a website https://oi****ne.com/ that has a digital archive of the magazines on https://oi****ne.com/di*****ve/ which is pointed to a sub-domain https://di****al.oi*****ne.com.
I am using Membership Pro to enable the put the magazine content behind a login wall. The members can register for free to get access to the content.

How can I do that?