How do I begin a Drag Block Script?

I am trying to remake my game and everything is going smoothly. I just made the droppers in Zednov's tycoon drop meshes and I made the button a surface gui that disappears on buy so I am proud of myself for finally editing a script!!!

Now I have no script yet sorry. I need to know how to begin a dragging script where you click and keep your mouse down but holding an apple and move it! Please Help me begin it!