Before you start, always remember to have the chainsaw's power cord disconnected or the fuel switch off when you are sharpening. Use a clamp to hold the chainsaw in position while you work. To sharpen, file from the inside of the tooth to the outside. The motion you should use is by starting flat and gradually lifting the blade up to get the edge. Three passes of the file will be enough for each tooth. Make sure you don't create a hook by twisting as you file. You'll be able to sharpen every second tooth on your first pass.