Custom Remote Question

I just bought an apple tv and loving it.

My set up is Apple TV > HDMI > Marantz AV Receiver which controls all my devices (cable box, blu-ray/dvd player and PS4).

I'm trying to set up Apple TV's custom remote so that I can use my Marantz remote with it but I'm kinda stuck as to which buttons I can use.

Arrows & select is easy, but I can't seem to use any of the Marantz's remote button for the Menu option.

Anyone with a similar set up out there that may be able to give me a suggestion? Thanks in advance!