You cant see it from the driving position. You can grope arount the telephone until the cursor finds it, or you can use left arriw until you are looking at the panel
When you are moving, place the throttle to off. Move the AFB lever to 160km/h, max setting. Look down beside your left knee as others have pointed out and turn the AFB switch to on. Move the AFB lever back to to speed setting you want, then move the throttle to 100%. To turn off AFB, throttle to off, AFB switch to off, AFB lever to 0.