You can enter at will. You can attend the "Teaching One, Teaching Two and Teaching Three" classes during class hours when you are not in Mingde, but Mingde needs the one-card of the National People's Congress. Peking university is also free to visit and attend classes, but it is best to have people you know, otherwise you can't find them. I am a student of the National People's Congress. You can ask me if you don't understand.