Well, first you need to UVW Map the model, so the texture will go on it correctly. There are a few tutorials on UVW Mapping, one of which I will give to you. But after that, you want to use a Plugin in called Texporter, that I will give you the link to at the end of post.
Once texporter renders out the maps you've made, you're going to open them up in the 2d program of your choise (Paint Shop Pro, Photoshop, I've even seen people use Microsoft Paint) and color the map you made using the polygon lines on it as a guide.
Texporter
UVW Unwrapping Tutorial
Hope this helps you out. Take care, and happy modelling