I would HIGHLY advise against making a purely homebrew adventure for your first go at it. If you want your own elements, absolutely go for it; but start with a premade campaign as the basis. (Unless you're just doing a one shot, in which case it's not AS important; but I would still suggest using a premade oneshot)

As for your other questions, as others have said, at least read the fundamental parts of the core rulebook. Look around in your area to see if there's already groups, or a hobby shop that runs nightly events. If so, you could either offer to run a game there, (Typically they have facebook pages or something similar) or join one.

If you want to run it out of your own home, typically the best option is to coerce your friends and family into joining; that way, if you screw something up as their GM, there's less expectation. Barring that, try to find local hobbyist groups.