Housebreaking a Shih Tzu takes months so be prepared and remain patient. You can choose to use the crate method of housebreaking or you can set aside a small piece of your home for your Shih Tzu. Either way is fine just be sure you pick one way and stay with it because you are in for the long haul and if you change anything then you will undo all you have done.
The crate method of Shih Tzu potty training is pretty simple it just takes time. Get a large crate and set it up with food and bedding and make the Shih Tzu comfortable in the crate. Play with it regularly but keep it locked in the crate while you are home. Every 45 minutes take it outside to use the designated toilet area.
They will not soil their own area so they will wait to be taken out as long as you do not keep them confined too long. Every 45 minutes take them out to the designated toilet area and show them praise if they go in that area. Shih Tzu dogs do not understand punishment so if they make a mess just clean it up and move on.
The other method is to choose a section of one room in the house and fence that area off as the Shih Tzu dog's living area. Then follow the same directions as the crate. It is important to not leave the Shih Tzu confined for too long as it will get confused and any housebreaking you have done will get undone quick.
After a while it will seem that your dog is beginning to understand Shih Tzu potty training and you can move on to the next step. Start moving their living area around the house and after a while they should begin to see that inside is for living and outside is for bathroom. They are very intelligent dogs but they are also stubborn so be very patient when you are starting to move their living area around.
Shih Tzu dogs do not understand punishment and punishing the dog for making a mess where it is not supposed to will only confuse it. If you have started to move the living area around the house and the dog starts to make a mess then return to the original living area and start over. Be patient and good luck.
Remember that they like to make the rules so it will take you a while to get them to understand that they need to follow the rules you set.