Well, you should definitely get started then.
What kind of ball is it? Who has been invited, and who is not welcome? Why? Describe some of the people at this ball thrown by the Capulets. Who are the hosts of the ball? Describe Juliet. Who does she come with? What do we know about her already? When does Romeo arrive? What do we know about him already? What happens when he arrives? What happens when Romeo and Juliet meet? Does anyone notice that an outsider has invited himself? Is anyhing done about it?
Do Romeo and Juliet speak to each other? What sort of things do they say? How does the ball scene end?
There, now you certainly have enough information to go on. Good luck.