Placing a UV Map onto the model.

Hey, I have recently picked up modeling again and decided I needed to learn to do the UV mapping.

I created a UV map with all the pieces cut out and placed on a single sheet. I then textured each piece and am ready to attach it to my model. How do I take this flat texture with all the different parts of the model and place it around my model?

I have read a bunch of tutorials, and they never show how to apply the texture once you create it.