The mission consists in point at a energy plant, and I think that the apache helicopter will shoot that energy plant, but doesn´t ocurr anything, and I am stock in that mission. Please tell me what to do to finish that boring mission, or in what consist that mission.

eu tbem nao consigo, os dois helicopteros sao demais, nao gonsigo destruir

You must place C4-explosives:
If you walk in from the front, walk to the left to these electricity..things.. and stand very close to it. If you stand very close, you will see C4 (it is yellow) and press X. (maybe hold down X a little longer). Get out and it will explode automatically.