Frame Market Parent Theme Child theme Question

I am trying to install this theme to work with the MarketPress Ecommerce lite app. The only issue I am running into right now, is that I have a forum that works with my current theme and the base version of WordPress. When I try and install Frame Market and go to visit the forum, which is a huge portion of my site, It is not there and mentions that I have to install/create a child theme. How do I do that so I can have my forum (wordpress standard plug in mingleforum). Any help would be greatly Appreciated.