First, you need to have the reader. You take the Commtech chip and move it over the bottom section of the reader (near the red "mark"). It takes a little practice actually, I remember having a hard time getting mine to work.
You can store up to 4 Commtech chips in the reader. I believe you hold the commtech over that red "mark" again and then press one of the 4 gray buttons until it makes a beep.