Here's the different parts of the body and what they're for. If you want to have the dimensions of the body showing there's a simple way to do that. I prefer Photoshop, but if you have Gimp it will work to I believe. Have one layer of the body template and create a new layer above it so you can draw over it and have the body template showing the dimensions. Don't want the template showing sometimes? Not a problem. Just click the eyeball on the layer to make it dissapear and click it again to make it come back. I've made plenty of bodies that turned out good in my opinion using this method. It takes practice and time, but you will learn it.