Child Theme, Signup and Homepage

Hi! I purchased the Whoop theme and I’m having a bit of trouble. You can seem my current site is being built at localdefenselawyers.com. I was hoping someone might be able to help me with these questions I have:

1. On the theme information it says that it recommends using the child theme. I don’t understand why and I’m not sure what this does. Do I need to uninstall the current theme and then install the child theme? Can someone help me understand this?

2. When I attempt to sign up it only gives me a login menu. How do I make it to where people have to pay to sign up?

3. I would really like the homepage to appear similar to the homepage of Yelp, but with only the above the fold area. In other words, I just want the homepage to feature a search bar, a menu and a sign in/sign up button. Is there a way to do this?

I really appreciate any help I can get on this. Thank you for your time.

Cheers,
Erick