Hi Lissie, this is almost no information at all, will be very unlikely that someone can help you with it. If you please could elaborate the issue, perhaps show some code that is not doing what you expected, and say what you expected, then probably someone could help. I’ve seen you asking questions like this and getting not much help, this is why 
we got no clue here.
Give a read in this pinned topic on how to ask questions and I’m sure you are going to get the help you want:
https://discourse.processing.org/t/guidelines-asking-questions/2147/8
cheers