Welcome Hirobo, lots of great people to help out here.
Finding the CG on heli is pretty easy. Pick up the heli with two fingers right where the blades grips are. If the heli hangs level, the CG is correct. If the heli is nose or tail heli, you'll have to make some adjustments. The easiest way is usually to adjust the position of the battery. Hope that helps.
Cheers,
Dino