Making the Tools Menu Appear

I was wondering how I should set this up.
Pressing the start button on Link? On Zelda?
What if I have two characters being controlled by two players at the same time? Would there be an issue?
I decided to set the menu with its own controller inputs.
I also want to make the menu itself a separate scene with dedicated controls to scroll through the items.
And of course, everything else in the game will have to be paused.
Something I don't know how to arrange yet.