Do you have a question about the Oregon CS1200 and is the answer not in the manual?
Place chainsaw on a flat surface, clean debris, remove cap, and pour 100 ml of bar and chain oil.
Loosen the chain tensioning dial and remove the side cover.
Loop the saw chain onto the bar and drive sprocket with cutters facing correctly.
Slide guide bar over alignment flange, with mounting stud through the bar slot.
Install side cover, ensuring tabs are seated, and lightly tighten side cover knob.
Adjust chain tensioning dial and fully tighten the side cover knob.
Slightly loosen the side cover release knob, but do not remove the cover.
Hold nose of guide bar and turn chain tensioning ring clockwise.
Tighten ring until lowest cutters contact the bar solidly.
Pull chain; it should snap back after being pulled 3 mm from the guide bar.
After use, allow chain to cool, unplug, and check tension periodically.