Position the telescope tube horizontally in the mount, or secure it horizontally on a flat surface. Ideally, this procedure should be done outside in daylight.
Stand 10 to 15 feet from the front of the tube and look at the primary mirror. When properly positioned, the primary mirror will appear circular and reflect an undistorted image of your face. A distorted image, or absence of your image, is an indication that the mirrors are seriously out of alignment.
Turn the primary mirror adjustment nuts at the base of the telescope tube, with the appropriate tool, alternately loosening and tightening the pair of nuts at each of the three positions, until the mirror is properly positioned. You can save time by having an assistant adjust the mirror while you observe the image.
Point the telescope to a bright area or surface (not the sun) and look into the empty eyepiece tube. Your eye must be centered in the tube when you perform a collimation. You should see an illuminated circle (reflection of the primary mirror) with an image of your eye near the center and three symmetric dark lines connecting it with the edge of the circle.
Loosen the adjustment screws on the secondary mirror holder.
Position the mirror so that it faces the eyepiece tube. Then, referring to step 4, alternately look in the tube and re-tighten the screws in such a way as to precisely center the image of your eye in the primary mirror reflection. The procedure becomes easier with experience.
Insert a medium power eyepiece (focal length 15 mm to 25 mm) into the eyepiece holder and tighten the thumbscrew(s).
Point the telescope to a moderately bright star and center it in the field of view. Polaris (the north star) is ideal because it will remain fixed in the field while you collimate the scope. If you choose another star, then you will need to make periodic centering adjustments.
Look in the eyepiece and turn the focusing knob to "defocus" (un-focus) the image until you see a pattern of concentric rings filling about half the field of view. The ring pattern and distribution of light within the ring pattern should both appear roughly symmetric. The bright dot you see at the center is a concentrated image of the star.
Perform adjustments, described in step 3, until the defocused image has the symmetry described in step 9.
Insert a high power eyepiece (focal length about nine mm) into the eyepiece holder, tighten, and repeat steps 9 and 10. The telescope is now collimated.