I’m still new to Lemmy as well, but I think subscribed it what you want. I scrolled through everything a lot in the beginning, once you see a community you like, click on their name and select join.
You can also search for communities and join them as well.
This adds that community to your subscribed feed. Is that what you are looking for?
Happy Bday! Thanks for the laughs! I always know its a quality joke when I see your user name!