As for contacting tutors, one way is to search their names online, find their email addresses and send emails. I'd better ask some questions by the way. But we must pay attention to the choice of questions. First, don't be too simple, it will make you ignorant. Second, don't be too difficult, it will make you aim high. It is best to ask questions related to the teacher's research direction, that is, what he likes.
If you can't find your email address online, try to find the teacher's phone number. It sounds difficult, but in fact it's not too difficult. In general, the department office of the school will have the contact information of the teacher. You can ask your classmates to help you look at it, or search the telephone number of the department office online, pretend that you are a student of this teacher and ask for the telephone number.
This is the first step. Contact the tutor. How to make your tutor have a good impression on you and how to make him provide some convenience when you take the postgraduate entrance examination depends on your teacher's personality and getting along with your.
What do you need to prepare for your major? I suggest you ask your seniors and sisters. If you can't find them, you can try to call the teacher for advice.
Remember, be sincere and modest.