Hover over your user icon in the navigation, and click "Submit photos" in the dropdown that appears. :) That link is only useful for logged-in folks though, so it's not great for sharing.
The general guidelines for the program are here: https://line-of-action.com/photo-bundle-policies although as pages to share it is on the boring side.
In terms of promotion, I'm working on a landing page that explains the program in a much more punchy way, specifically as something that can be shared on social media. Gimme a few weeks here to settle the moving dust and I'll have that out for everyone. It'll most definitely end up in the news. :)