Where is the button!

I can’t find the “Select allunits Button.” In Halo Wars it was Left Bumper. Now I can’t find it. Please help.

> 2535416390289203;1:
> I can’t find the “Select allunits Button.” In Halo Wars it was Left Bumper. Now I can’t find it. Please help.

If you press and hold RB it should select all units

thx