How do I create a "click and crush" kind of thing for my project?

Hi everyone.
My project is a "candy-crush like" game (very watered down version), where the player has to click on the objects to earn points.
What I don't understand is, how do I make it so that a user can click on the object so that they are crushed, and new candy comes in?
I'm having a really hard time with this....i can't seem to do it for some reason! Please help me!

Thank you so much!