I just thought I would update this post in the hope that it would help others with this same problem.
The first mechanic told me I needed to replace the water pump, as it was leaking and causing the belt to slip off. So I had him replace it, along with the iders and the tension pulley.
Within a year, it started slipping off again. I took it back, and he told me that it was the water pump. Hmmm...you just replaced it a few months ago, how could that be? Well, we got it replaced, no charge for parts. I was charged for labor. He also replaced the timing belt for me, as it was beyond the maintenance schedule.
Guess what...it started slipping off again. I took it to another mechanic, in another town (we moved). Guess what his diagnosis was? Water pump. I told him that we had already had it replaced twice. He swore up and down that he saw cooling leaking out the weep hole. I had him replace it with a motorcraft (original equipment part). Two weeks later, it slipped off again.
I finally found someone that would listen to me. He pressure tested the coolant system with die...and found a small leak in the head gasket. It was spraying coolant onto the belts. After replacing the head gasket, everything has been great for 6 months.
During this whole ordeal, I got pretty good at putting this belt on. I hope I don't need to do it again.
And to answer my original question, just turn the bolt counter clockwise, and the tension is taken off the belt. Sometimes the simplest questions can be the hardest to answer.
oh yeah, and the haynes manual? I do have several of them, and 9 times out of 10, they don't have the information that I need. I'm struggling with the heater on this car now, can't get the diverter to work. I'll cover that in another post, tho....and the haynes manual doesn't cover it....