It is best to start training as early as possible. 2 months is a good time to begin if not sooner. Hopefully the breeder has already done some paper training.

Jack Russells are very social and like to be with the family and see what you are doing.

So the best way to train is to have them in a place where you can see them and they can see you. Do not let them have the full run of the house. And do not let them feel they are in control of thing. The best way to do this is to have a hook with a dog clip to attach their leash near where you are working or watching television. It is best not to be in a carpeted area of the house. Make the leash just long enough that your Jack Russell Puppy can reach his newspaper on the floor, his little bed and his food and water without turning things over or getting tangled in the leash. He will not like this for a start and may struggle and make a lot of noise. Reassure him that this is not punishment. This is HIS place in the house and he is under control. When he is calm reward him with a toy or treat. This is a good position to teach him to sit. At regular intervals take him out to the area where he is suppose to go potty. Walk him directly so he can let you know later when he wants to go. When there is an accident don't scold him or speak loudly... just scoop it up in the newspaper and take it to the potty area and let him know that is where he is suppose to do that. There will be accidents up until about 6 months. But if you take control at the very beginning life will be much easier for everyone. Also it will be easier to tech him simple commands and not to climb on furniture and the difference between his toys and your 'toys' when his is not given free run of the house and keep in a contained environment. At night he can be put in his kennel to sleep and always take him out to potty as soon as he wakes. Teach the children not to play with him until he is taken to his spot.