I assume you're playing part one of the Armageddon Eclair, and that the little robot you're trying to shoot is the one trying to kill you with a chainsaw.
Cycle through your cursors until you get to the one that looks like a hand holding a gun. The hotspot for that cursor is on the end of the gun barrel. Click it on the little robot and the hero should shoot the robot. Just make sure you do it before he reaches you!
Thanks for playing my game.