What have you tried? You MUST try to write the code yourself.
You will need a setup() and draw() function. In setup(), you must call size(). Start with that!
Since you will have many dots on the screen, write a Dot class.
Where will a dot be? What color will a dot be? Can you make a dot? Can you draw a dot? Can you have many dots?
I’m closing this thread, as it’s pretty much a duplicate of this one:
It’s really hard to help with general “how do I do this” type questions. Please try to break your problem down into smaller steps and take those steps on one at a time.
You might also want to read through this guide: