In this case, you know the number of degrees, but don’t know what "aspect" to face (what direction should I face?).
Let’s assume you wish to face true north (zero degrees).
Compass without adjustable declination: turn the compass dial until zero is at the index line. If local declination is positive, subtract this amount from zero on the compass ring (turn the dial clockwise). If local declination is negative, add this amount to zero on the compass ring (turn the dial counter-clockwise). With the direction of travel arrow pointing directly away from you, rotate your body and compass together in one motion until the red magnetic needle overlays the orienting arrow. You are now facing true north.
Compass with adjustable declination: turn the compass dial to zero. If you haven’t done so already, adjust the declination so the orienting arrow deviates from the compass ring’s north indicator by the amount & direction of local magnetic declination With the direction of travel arrow point directly away from you, rotate your body and compass together in one motion until the red magnetic needle overlays the orienting arrow. You are now facing true north.
