Need help with buttons

I want to play Yume Nikki, but I need the “s” key. How do I get a button to be an “S” key?

Do you play on Android?

While ingame press “Back” on your phone to open the Player menu. Select “Edit Layout” and add a “Shift” button. Shift is (S)

I mean like the “S” key. Not shift or anything. Like the letter S. And yes I’m on android.

What is the S-key supposed to do in Yume Nikki?

Arrow keys - movement
Z - action; confirm
X - menu; cancel
1 - use effect ability
3 - cancel effect ability
5 - drop effect
9 - wake up