I've never used one with my animals, but if you want to use it, try getting him used to it by clickclickclick - give a treat, clickclickclick - give a treat. Make him think everytime he hears the click he will get a treat, then as he starts responding to the clicking favorably, give less treats until it is just the click.
Thanks so much for the info. Im still working on getting him used to it. And hes doing well. Thats one of the few bad things about a rescue, knowing whats happened in thier past. He has made amazing progress in his obediance since I got him and he knows "gooooood Booy" and rejoices with wild wiggling and tail wagging knowing hes done well.