Hiya,
The Security / User options in Revolution are amazingly flexible. However that also means they’re slightly hard to get a grip on when you’re just starting with MODx.
If you’re using Revolution you will need to set up the right ACLs for your resource groups and contexts. Here’s a tutorial you could use:
http://rtfm.modx.com/display/revolution20/Making+Member-Only+Pages Registering/logging in can easily be done with the Login addon.
While Evolution’s security set is much easier and less advanced then the one in Revolution, for a simple member area that should suffice.
In brief, you will need to make two document groups, one for each hidden page, and link these to two user groups which the users can be assigned to. Since you’re linking these you can determine which they can view.
If you want to allow users to sign up, you can use WebSignup - perhaps two instances on different pages where they can sign up for the different user groups. If you want to allow your client to sign them up, they can do that from the manager. WebloginPE is good for your other user needs.