Take the headset cord out of the telephone and insert the pre-installed cord from the Busylight box into the telephone instead.
Insert the headset cord (that was in the telephone before) in the front of the Busylight box.
Insert the cord for the Busylight lamp into the Busylight box and mount the lamp on your screen (or another visible place) with the round tape. Avoid placing the lamp in direct sunlight.
Connect power to the Busylight box with the USB cord.