Creating Themes & Selling

Hello Xenforo,

I wasn't sure where to put this thread so I hope it's in the correct section.
I've been using Xenforo for a while now, I'm no longer continuing my forum but I really enjoyed creating themes and getting into that side of it.

I was wondering how I can go about creating themes and putting them up here to sell, or as free themes since I've seen them around.

I'd really appreciate any advice, I can't seem to find any answers.

Thanks for reading.