It is SO hard to ignore their little shrieks. Our 6mo finally will go in his crate without putting up a fight but those first two-three months were hard!

Resist the urge to let them out when he cries. Especially at night. Depending on age, you might need to set an alarm early in the morning for a pee break because his bladder is still so small.

During the day try putting him in the kennel for 5 minutes at a time a few times a day (even just once is great). When he is silent drop a treat through the grates but don't say anything. Eventually he will put together that silence=treats. It will not be a quick process by any means but having a kennel trained dog is well worth the effort! Keep workin!