Hi!
...I know you put a bell by you rdoor and when you go out, you ring it. When you come in, and if they did something outside, you ring the bell again. Is that pretty much it?
Not exactly - or at least, ringing the bell on the way back in is not needed, and actually is likely to be counterproductive. It should be rung *only* immediately prior to going OUT.
What bell training is is a means for
the dog to let you know that he/she wants to go outside. Dogs are pretty good at learning in terms of cause/effect relationships. Thus, if you have the dog ring the bell (just take his paw and assist him to ring it) prior to opening the door - EVERY time you're going to open the door to let/take him out it, then he will learn that ringing that bell *causes* you to open the door. Not long after that, he's going to start ringing it every time he
wants to go outside.
Can you see why ringing it on the way back in would be counterproductive? If he's ringing it and you're not opening the door - how's he going to come to the conclusion that this is what makes you open the door? You'd be giving mixed signals

So better to stick simply with having him ring it prior to going out.
What bell training isn't is housetraining. It does not teach the dog that pottying is an outdoor activity - you still have to train that. Rather, it is purely and simply a means of providing the dog with a way of giving you an audible signal that he would like to go outside. For whatever reason.
Of course, once the dog has firmly got the idea that ringing the bell = you opening the door, then you could start to be discriminating about when you answer the request and when you don't. So when you're absolutely certain that he's ringing it just because he wants out to play and hasn't any need at all to potty, you might ignore it. But in the initial stages, it is wise to answer every time so that the cause-effect relationship gets instilled in his mind. Combining that with standard potty training (outside frequently, lots of praise as he
starts to pee or poop) is generally a very effective method.