PLEASE look for yourself first. There are tutorials that use reference images out there (you probably wont find a tutorial only on reference images because they are quite basic.)
Simply by searching google for "anim8or reference image" I found this tutorial:
http://members.lycos.nl/jonim8or/head_tut.htmlIt uses reference images and shows you how to put them into a project step by step. I'm sure there are plenty more tutorials doing that.
This is a one time lesson, but SEARCH FOR YOURSELF FIRST. Whether it be google or on the forums you can usually find what you're looking for. AFTER you search yourself ask on the forums.