Set the switches on the bottom of the base to DHSG and 1
Grab the Y-cable of the EHS. Connect the single end to the AUX port on your telephone
Connect larger cable of the Y-end to the AUX port on Leitner base. Smaller end goes into green TEL port on the base
Plug your power cord back in
*For Mitel phones, you may need to enable DHSG headset mode in your phone settings. This typically is found under "Headset" in your phone's audio settings