Debbie, here's what the FAQ section of the BV site states with regards to ceiling fans and vaulted ceilings.
What does it take to put up a ceiling fan on a vaulted ceiling? Depending if you already have a fixture or not. If you do your wiring is already there. But, I would bet that the box does not meet NEC code. A normal ceiling box will not properly support the fan and the torque of the motor. They sell a kit so you can remove the existing box and replace it with an approved box. Try your home center or electrical contractor. If you don't already have a fixture present, you'll have to install an approved box and wiring. If you're not familiar with this type of work, call a skilled contractor. Ceiling fan manufacturers sell a variety of accessories for sloped and vaulted ceilings.