Ok… lots of great advice here. But a lot
Of is being given for a “more than beginner”. You literally just signed up for your first race. But I’ve got some seasoned advice to give you for your first one.
Finish. Make your own plan and STICKING to it. Train to make sure you can complete the distance of each discipline. (Build the vine slowly and incrementally with a recovery week every 4 weeks where you do easy stuff or hardly anything.) Once you’ve gone and done the first race and you want to sign up for another one, then let’s talk structured training.
Caveat: I wouldn’t ever give this advice to someone raving a full or half for their first race. But I would also recommend that they never do one of those distances for their first race either.