How to create a Membership area
Make sure you have created your products that people will buy in order to get access to this membership area.
Go to Websites/Sites > Create New Project > Membership Site
This will auto generate the following pages:
-Login
-Forgotten Password
-Welcome
-Index/Home
The login and forgotten password pages are fairly self explanatory, but rather than relying on a bog standard design, you can completely design your own login and forgotten password pages.
If you want the page design to be almost identical, then create the login page, duplicate it, and add the "Forgotten password" element, and delete the original "Forgotten password page".
You can create as many additional pages as you like inside the Membership site, but you will need to go into the Membership app in the site builder and add all the pages you want securing to the specific Membership app.
There's a video walkthrough in the Tutorials section, that's highly recommended viewing.