If the display says SYS INFO AVAIL you don’t need to do anything, otherwise use the ‘Yes’ button or Data Entry slider to change it to SYS INFO AVAIL If ‘MIDI Ch=1’ is displayed you don’t need to do anything, otherwise use the ‘Yes’ button or Data Entry slider to change it to 1.
Connect one from the MIDI OUT of your interface to the MIDI IN of your DX7. You need an audio interface that connects to your Mac and that has MIDI IN and MIDI OUT 5-pin ports. I hear MIDI Ox is a great app for non-Mac users.
These instructions won’t work in full on the subsequent models (DX7s, DX7 II, DX7 IIFD etc)