I thought it just required posting something with the relevant term. But Reddit still confuses me as a platform and I cant say I follow it any.
From some of the SEO stuff I vaguely recall, I think you just need to post a link/pic whatever to a target subreddit ... goldcoin seems to exist as it could be searched on.
Also keyword searches get posted with all relative links and get picked up/indexed by other systems and crawlers. FWIW.
Maybe just an announcement posting of the Android app as a test?