Yay .joseph! You could do a sticker reward system. Make a chart. Every time he goes in the potty, he gets a sticker on his chart. 5 stickers = a new (inexpensive) toy, or something like that. Make it fun, and make sure he sees that good things come from going in the potty. He might be a little young, I don't know, but you could try it! You could be like "yaaaay you went tinkle in the potty! Let's put a sticker on your chart!" and make sure that he helps you or watches you put the sticker up
immediately after he goes in the potty, otherwise he might forget about why he's getting a sticker. Tell him what a big boy he is. Stuff like that. Positive reinforcement, baby girl! Mm hmm!
...but like I said, he might be a little bit young to understand? I guess it depends on your son?

anyway it's an idea!