What have you written so far? I suggest to start drawing the circles at the right places, unconditionally. Then, in mousePressed(), check the coordinates of mouseX and mouseY against the given areas.

I'm fairly new in this program and i dont really have a background in programming. This is our first assignment so I would appreciate if you help me get and understand the codes.

read this
http://www.processing.org/learning/drawing/

and this

http://www.processing.org/learning/overview/

have a look here
http://www.processing.org/reference/ellipse_.html

or there:
http://www.processing.org/reference/mouseX.html

copy those, make them run as your own program and then try to figure it out - it's fun!

Greetings, Chrisir