Talk to the folks at nursery; you don't have to do things their way, but it'll be easier for all if you do. The fact that your lo has seen other children do it means that he probably wants to join in.
Our approach has been 100% child-led. We started with "Mummy needs to wee, do you need to wee?" and then our DS seeing me use the toilet before him having a go. The idea was for him to learn that a nappy is for if you can't get to the toilet in time (i.e. it's okay to wee in your nappy), but the toilet is where it goes. He was young enough when we started (14 months) that he hadn't yet developed wee/poo awareness, but through timing (first think in the morning/after a nap) he quickly had his first wee on the toilet and got such a fright when it came out he said "uh-oh uh-oh" the whole time, and every time he weed for a week!
Occasionally he'll refuse to go on the toilet (which we never fought) and sometimes after sitting on the toilet will then pee on the floor or poo in a nappy but it's because he didn't know it was coming or we took him off too soon rather than some kind of resistance. Our attitude in the beginning was one of every nappy spared was a bonus, rather than every nappy soiled was a trial. We knew we were starting young and it was imperative we had realistic expectations.
DS moved up to the toddler classroom at 15 months and at his nursery, potty training isn't optional. Kids are all in pull-ups and they all go on the toilet at least every two hours. When they make the change to pants, they start out going every half hour. There's no pushing, lots of opportunity to see other kids on the toilet showing them it's okay and making them want to "play" too.
We've had to have words about making sure they let him stay on the toilet long enough because him being so young still, it takes him a while to get a wee or a poo out, even if he knows he has to go. Sometimes 2-3 minutes on a wee, especially first of the morning (which can also sneak up on him and has landed on the floor a time or two) and sometimes over 5 minutes on a poo. We have great one-on-one play time in the bathroom, so he's rarely asking to come off the toilet, even when he's done!
He's now 17 months and asking about half the time when he needs to wee, and most times when he needs to poo, nasty teething tummy upsets aside. I've read in a child development book that the parts of the brain that have to mature for potty training are related to those that have to mature for walking. DS started walking before 9 months, so it makes sense that he was ready to start earlier than others.
He can't yet remove his pants himself, and can't get onto the toilet himself, but he certainly can hold it in (sometimes). He's held in a poo for an hour (between first asking and finally getting home and onto the toilet - his preference to hold it rather than poo in the nappy) and half an hour on a wee.
HTH and GL.