Hello. I’m usually going by foot or car.
Technically I think anyone can post to the #film page. The tabs under the tagged film section has spots for “Featured,” “Popular” and “All” posts. The post under the “Featured” tab are the ones that editors of the section have promoted (posts that have the little blue tag at the bottom of them). The “Popular” tab are featured posts that have the most “notes” (reblogs and “likes”). The “All” section is just a collection of different posts that haven’t been tagged but pertain (at least somewhat) to the section. I can’t speak for all editors of the section but usually what I do is go to the #film page, click the “All” tab and browse what’s on there. When I see something original or different or something that just tickles my fancy I promote it. I assume your question is more along the lines of how can you get featured on the film page, to which I can only say keep posting original and exciting material that you come across or come up with and hope it gets seen. (Disclaimer: a lot of this answer persists of educated guesses)