On the main 'LISTING' page center is a link:
under: Auctiva's Custom Templates; Create
You can insert your html code into the box. You'll have to use the picture code (last post) here:
https://community.auctiva.com/eve/forums/a/tpc/f/455609321/m/3421062911/p/2
MAKE SURE YOU HAVE THE HTML button? selected!
get back if you've more problems.