How to require Email Verification on registration
First install this free plugin: https://wordpress.org/plugins/user-verification/
Create a new Page in your WordPress site, and name it something like "Verify account".
In the content area of the new page, place this shortcode
Next edit the User → User Verification as shown below
You can ignore all other settings and tabs on this page as they don't currently seem to apply to MemberPress.
Make sure also that you have "Enable domain block" and "Enable username block" options set to "No" in the "Spam Protection" tab if you don't need these features. By default, they are set to "Yes" which may cause errors on the signup page.
Save the settings and that's it! Pretty easy eh? Now your members will have to click a link in their email before they will be allowed to login to your site after joining.