I need a diagram to know how to put my belts on a 2001 mazda 626

The best place to start is investing in a "Haynes" or "Chilton" manual for the specific make/model/year. often you can find such a book at your local library.

Barring that, I can tell you of some Mazda expeience I had on an MX 6 which may be quite similar. First of all, and this is IMPORTANT, make a sketch of the "layout" of the large serpentime belt that goes around the inner race of the main crankshaft pulley (and everything else other than the AC compressor). Note that there is an "idler" pulley, something like 4 inches across, around which the smooth outside of the serpentine belt goes. Notice also on the compressor, there is a brass-colored post that sticks out ending in a 10mm hex. This needs to be turned several turns counterclockwise to loosen the tension; it is also necessary to loosen the compressor mounting bolt that maintains the tension (loosen them all if you are not sure which one, just remember to re-tighten). Now, go ahead and loosen/remove the stud holding the idler pulley onto the front of the engine, and remove the pulley and its washer. The belt should come right off. Install the new belt, reinstall the pulley making sure the new belt is "tracked" right according to the sketch you made before you removed it, retighten the compressor 10mm hex-head tensioner until there is between 1/2 and 1 inch of 'give' in the logest stretch of belt when you push/pull on it with a few pounds of force., Lock down any bolts you may have loosened on the compressor. With the engine in neutral, turn the engine by hand, clockwise, using a socket wrench on the main pulley bolt to see that things "look" right and maintain their tension. Then start the engine and let it idle for a bit and examine that things still look right.