start simple, do chest for day 1,back for day 2,leg for day 3 in that order and take a rest day after if you're sore(you'll be sore if it's your first time, it'll disappear once you've become consistent). Do around 5 different workouts starting with small weights with 3 sets of 10 repetitions each. If you've got a spotter then you can do failure if you want(do the workout until you can't anymore)
I'm gonna try and convince my dad to go to the gym with me, so imma screenshot this