1.) Go through Chapter 12 (pg. 631-635) to get familiar with MEL.
2.) Complete the following tutorial. Note: Make sure you use polygon spheres and not NURBS spheres. For MEL syntax select Help > Maya Help > Using Maya > General > MEL and Expressions > Syntax. When you are done you should have something similar to below.
3.) Once you've completed part 2, go creative. Try modeling another object of your choice with MEL. The only requirements are that you use at least one for loop and an object other than a sphere.