You have to create a human model that doesn't have a face on the texture, then attach your face model to his head. For example, here's a faceless steve skin that you can use with the face model:
As you can see, the only thing you have to make youself is removing the face of the skin you want to use. Once you created a human with your texture, parent the face model to the head (= attach it to the head of the human model).