Potty training my 3yo boy. HELP


He is showing almost all the readiness signs to be potty trained so we started today. He has been really excited about his new underwear and will sit on the toilet but will not pee or poop on the toilet. I know it’s just the first day but I’m just wondering if he’s still not ready???? How do you know? Ugh I’m just frustrated. Not with him but just like how on earth do people potty train??? 😩😭