How create shortcut key for the standalone viewer?

default shortcut key is page down and page up key for go to next/previous photo, I want to change the key with right arrow / left arrow

Settings / Customize / Keys.

I am in here, now …… how to do?

That looks like Opus 11 not 12?

(Your profile says 12, and you need to be using that version to edit viewer hotkeys.)

Thanks for the reply.