If you want to approve all new users before they can actually login and access their accounts/content, follow the steps below.
1. Download and install the New User Approve plugin.
2. Download and install the New User Approve - Ignore Password Reset plugin. (By default the New User Approve plugin changes the members password to a random one when they signup. Since MemberPress allows the member to setup their own password, we want to make sure we don't override it. That's what this plugin does.)
3. That's it! Anytime a new member signs up on your site, they will be held in a moderation queue until you Approve their account via the Dashboard -> Users -> Approve New Users menu.