what everyone is saying is pretty much true...wait, he's not ready. however, i personally think you can help him get ready by talking about it in a non-threatening, non-nagging way, everyday. and if you feel comfortable, use your husband and/or older sons (if you have them) to show him how it works.
a friend gave me a potty training dvd (had elmo on it) but my boy wasn't interested so one day, i turned up my heater so he could be naked from waist down, rolled up my rug, put his potty in front of the tv with lots of books, games and toys and we spent the entire day in my living room. we did this when he was 2.5. we had the nice cushy kind of potty from first year so it made sitting a lot easier (http://www.smarter.com/the-first-years-soft-trainer-seat/.... after couple of accidents, he kind of got it so we switched to pull-ups. personally, the 'cool wet feeling you're supposed to get if you have an accident in the pull-up' dont work. my boy didn't care, as most boys don't.
i would ask him every 15-30 minutes, "do you have to go potty? do you have to pee? do you want to try? let's try...you'll tell mommy, right?" i know it was annoying but so what? after about 6 months of mostly successes, we had him pee standing up. for a boy, it's huge! my sister had gotten me a peter potty urinal (best thing ever!) and i painted a bulls eye where he could point and he loved it! my husband was the one to train him on that (i have no idea where or how to hold it!). now that he's a little over 4, he is potty trained and poopy trained but he still has accidents because he doesn't want to stop playing or watching tv to go pee so my husband will have races with him to see who can pee first and/or we love checking out new bathrooms.
it's hard but hang in there! good luck.