how do u calabrate a compass on a 2000 bravada?

Find a large parking lot and drive the vehicle in a complete circle three consecutive times.

do u need to hold anything down or press anything in

No, just do 3 complete circles, in the same direction, without stopping.

thank you very much one more thing, do u know where i could get a filler neck hose for that same vechile?

Or have some fun, find a muddy field and do some donuts. The compass is self calibrating to magnetic north, not true north, unlike earlier models that can be calibrated to true north. The self calibratrion to magnetic north rather than true north is considered more "user friendly" since the compass constanly recalibrates itself on a long trip like across country while the older models had to be manually recalibrated often during a long trip east to west. Parking in garages or structures with a lot of rebar or other steel or iron will throw the calibration off. It will recalibrate on it's own after about 20 miles of normal driving but spining some donuts is faster and more fun.