Your BF making the phone call is a very good 1st step. Now he needs to follow through. That is the toughest part for him. If he can make it to the first appointment and then to the next two or three, he'll be well on his way and will most likely be sticking around.
The first "ice breaking" session is critical, but the follow up is probably the most important. For you, all you can do is to try and reassure him that you will be there to support him through his therapy. Make sure he realizes there isn't anyone who will love and support him better through all of this than you.
Remember you can't do it for him, but you can clearly let it be known that you're there to pick him up when he falls and reset him on the path his therapy will lay out for him.
