I’ve trained three boys all by 2 and 1/2 – the first few days will be a stress – don’t get stressed!!!
Give him a lot to drink and sit as much as possible by the toilet (or take every five minutes)(I used a potty so he can be wherever I was – people either love it or hate it.
It is going to take a few days no matter what – once you know that you won’t give up and once he is in underwear – he will probably have an accident or two per day for the first few weeks.
The main thing is just be consistent and give it time – don’t try to do too much else at the same time – it never works.