Although Podpage doesn't have any built in membership features, we have one way for you create an area on your website that is only accessible to members: password protected custom pages.
When creating a custom page on your website (Website → Page Designer → Create New Page), you have the option of password protecting the page:
If you enter a password there, when someone goes to access the page, they'll first be asked to enter a password.
Only people with the password can access the page. So, this is an area where you can share the password with your members and only they can access the content.
Hope that helps!