Well, you could spend money here or...

The app itself is fine although rather unresponsive. Im not going to go into all its little problems because lots of other reviews have done that extensively.
Would I recommend it? No. What I would recommend is going to the "miners need cool shoes" website, it is excellent, and free. Much better for making custom skins and looking at preexisting ones.

Mac101 about Miners Need Cool Shoes, v1