Add free subdomain from Freedns.afraid.org to Cloudflare

First of all, i'm nowhere near an expert (Never used cloudflare before).

I want to expose my application through a cloud flare reverse proxy. I want to use a free subdomain from freedns.afraid.org. How would i approach this, is this even possible? (From what i can see i can enter a NS entry for the subdomain in the FreeDNS web interface)

Thanks in advance