Need help setting up freedns.afraid.org custom DDNS

I just bought a RT-AC68P and have installed Asuswrt-Merlin 380.57 and have been trying to get everything configured today. I am coming from Shibby Tomato and have always been able to update my freedns.afriad.org DDNS account right from my router, so I wanted to do the same with Asuswrt-Merlin.

I've found the right documentation concerning setting this up, and I followed the directions the best I knew how, but it's not...

Need help setting up freedns.afraid.org custom DDNS