1, introverts have a great feature that they are not good at talking and don't know how to express themselves. But not being good at expressing yourself doesn't mean you don't have any thoughts in your heart. So, what you have to do now is to express your inner thoughts truthfully.
If you are a student, I think the best way to change yourself is to take an active part in class activities and answer questions all the time. This is not only a good way to test your knowledge reserve, but also a good way to exercise your courage to speak and learn organizational language.
3, I think, there is a better point is to expand their friends, through exchanges and interactions with friends, on the one hand, let themselves learn how to express themselves, on the other hand, the growth in interpersonal relationships can help them quickly mature and cheerful.
Bless you
Ai ren a Bao