How do new users sign up & can they be vetted w/a recaptcha?

Hello. I have two websites on your plugin and they work great, but I can’t figure out how new users are creating accounts. I don’t have the Login page connected to any of my nav menus and what’s worse, all those signing up appear to be fake/bot accounts just from the look of the email addresses. Is there a way to connect up a Google recaptcha to confirm valid email addys? Thanks for your help!

The page I need help with: [log in to see the link]