which button activates the remote sniper rifle

When I get to the level where we are attacking the ball park, the first time I need the REMOTE SNIPER RIFLE, it shows up automatically.

Afterwards, When I am told to use the REMOTE SNIPER RIFLE the screen indicates a button to push, but I can't find it on my console.  I have pushed every button, and nothing happens.

Please help.  I want to move forward with the game.

Thanks,

king_cobra@sbcglobal.net