Hello Robert,
If the projector is mounted, on the left side of the PRM-30 you will see some cables going into the projector that are covered and protected by a silver cover. Remove the screws that are holding the cover in place and you will see the HDMI port there. There is an illustration in the PRM-30 User Manual located on our knowledge base at www.prometheankb.com. (case# 291012)
Thanks!