Everyone has their own tips and tricks on how to potty train their little boy. Because boys develop slower than girls they may take longer to do a lot of basic things and using the potty is one of them.
The first thing to do in most cases is to buy a potty and a few pairs of underpants. Let him get used to seeing the potty and sitting on it. Introduce him to the basic method by letting him go with daddy or a male relative for some practical training. Before you expect him to do anything himself make sure he knows the words you use for the various functions such as pee and poo and make sure you use these words all the time so as not to confuse him.
When you are going to have time to sit with your child swap his diaper for pants and take him back and forth to the potty, letting him get used to it. Make it almost like a game and whatever you do don't scold him if he doesn't get it right for a while. Do however give him a reward when he does and make a big fuss of him. This lets him know you are pleased with him and will give him the confidence to use it more often.