Explain Controller Symbol for Expedition

I would love to have an explanation of what the expedition "place explosives" symbol is for controller. Up + down on the D pad at the same time? Up and then down? What is this symbol. Nothing has worked for placing the explosives. An in-game guide for controller symbols and actions in general would be good.

Figured it out. I had "activate secondary skill slot" bound to down on the D-pad. Since explosive is "that + up on the d-pad" it wanted me to do an impossible act. Maybe should fix/explain that.