Ok i need Cod Bo Wii Help!!!!?

Ok i have to infiltrate baikonur cosmodrome...Idk what that means...BUT ANYWAYZ im at a point where i have to hide beside this red pipe and dunk down so these helicopters don't see me! AND IDK HOW TO DUNK!!!!!! im using my wii zapper. if that helps... PLZ HELP i keep on having to run then the helicopters shoot me and there is no way to outrun them! Plz plz plz help i really need HELP!!!!!