Not sure where you're seeing them... it's always been in the microblog section, you can also follow individuals on Mastodon. They also come up in searches and hashtags.
Don't be intimidated, interaction works just fine!
Normally if nobody from an instance has subscribed it doesn't show up in searches from that instance. You have to manually type the exact url and subscribe that way. Once one person has done it, it will show up.
Unclassified microblogs (e.g. from Mastodon users) usually end up in random, but I'm not sure how to post them intentionally since I don't use the microblog feature much. Hopefully someone else can chime in with an answer for this.
I can answer this, go to your own profile, choose add new post (not thread) and then from the "select a magazine" dropdown choose random. Then just use your @ tag like normal if you want to @ someone in the fediverse.