How do you remove the bolt from an H and R model 765 Pioneer 22 rifle?

Best bet is to take it to a gunsmith.

Wrong answer! You can do it yourself. First remove the action from the stock . There is a single, large screw in the underside of the stock, forward of the trigger guard. The barrel and action come out as one piece. Then open the bolt and make sure the safety is off (fire). The next part needs three hands: simultaneously pull back on the trigger, pull the bolt back, and pull down on the sear. The sear is the flat angled piece just in front of the trigger, but behind the cutout for the lifter. The very front of the trigger fits into a notch in the sear.

To reinstall the bolt, just slide it back in while you hold the trigger back.

IMPORTANT! Don't twist the bolt while it is out of the action. The bolt body has three sections and if they are not in the proper alignment, the bolt will not go back in. And I don't think I can describe how to get the bolt back together. Have fun!