Then you hold the compass at eye level. All good woods compasses feature sights, much like a rifle's iron sights, with a line drawn on the compass between the sights. You aim the compass at the mountain peak. Then, holding the compass absolutely still in one hand, you use your other hand to turn the compass's face until north lines up with the needle. The pitfall of compass work is declination, the difference between true north and magnetic north.
Magnetic north lies north of Canada in the islands of the Arctic Ocean.
At the bottom of each USGS topo map is a little printed angle that shows the difference between magnetic and true north in the area shown by the map. Where I live, magnetic north is 18 degrees east of true north. If you're using a nonadjustable compass, you have to turn it in your hand to adjust for declination. You must be sure to turn the right way, which is why adjustable compasses are better. When in flat country, take a compass bearing every time your course changes and pencil in your route on the map.