I gotten to where if I hit the "Run" button it just generates a random number and I've tried using if(Greenfoot.mouseClicked(This)) but I think I failed at that as well. I would show the code but theres not much except the objects I made such as the "+", "=", and the boxes that hold the numbers.

At least show the world class, which should show how your objects are created. It would be best to have attempted code for what you are having problems with included in the class so one can get a general idea of what you are trying to do. Explain where you are having difficulty and how is should be compared to how it is currently behaving.