Potty training help

Ryan • I`m a nanny for two great boys. I also like to draw in my free time and plan on going to art school in August.
I'm a nanny. The parents and I think it's time the oldest is potty trained. He is almost 3. He use to be a crying mess when we put him on the potty but now I say let's go potty and he runs to the potty is super excited. I understand potty training takes more than a day. 
Here is what happens. He was in big boy pants because he hates being wet we thought once he realize that goin in his pants made him wet he wouldn't want to go in his pants. He doesn't do anything before he goes potty he quits moving when he goes. I was taking him to the potty every 5-10 min so he won't pee on the floor but he never goes potty. I picked him up in the middle of him peeing in his pants and he stopped. When I put him on the potty he sat there for 5 min an nothing so I figured he was done. Not even a min later he peed again. He did this 3times in less than an hour. I had to put him back in diapers cuz they don't have pull ups or anymore clean big boy pants (doesn't bother me cuz I also am taking care of an 8month old and can't spend all day cleaning pee up off the floor) I don't think he understands what he is suppose to do on the potty. Nor do I know how to teach him.     
I've never had to potty train a kid before so I am completely lost. Please help