Answer:
Antes:
Tu tienes que llegar a tiempo para el baile. (You need to get to the dance in time)
Para entrar al baile tu tienes que traer un traje o vestido. (You need to bring a suit or a dress)
PS: If that one is too complicated use this one
Tu tienes que traer ropa buena (You need to bring good clothes)
Durante:
Tu tienes que comportarte bien. (You need to behave well)
Tu tienes que bailar. (You need to dance)
Tienes que divertirte! (You need to have fun!)
Despues:
Tu tienes que salir a las 10:30PM (You need to leave at 10:30 pm)
El baile termina a las 10:30PM (The dance ends at 10:30PM)
I ADDED EXTRA SENTENCES SO YOU CAN CHOOSE THE ONES YOU LIKE.