When I first brought home my Shih Tzu puppy, I introduced him to his crate. I had placed a blanket, some toys and some treats inside to make it happy and inviting.
During the day, I left the crate door open so he could go and play with his toys or take a nap whenever he wanted.
Every night, I took my Shih Tzu puppy out to pee and then tucked him into his kennel for the night. I left him alone, but did check on him if I found he sounded panicky or like he needed to go pee.
After a few nights of whining, my Shih Tzu puppy settled down and started to sleep into the morning hours.