A chainsaw is not really necessary - it only makes the job faster. Cut the wedge about 2 feet off the ground (dirt on the bark lower than that dulls a blade quickly). Cut the wedge on the side you wish the tree to fall,with the slant on the lower part of the wedge, and a horizontal cut on the top edge of the wedge about 2/3 of the diameter through. Then make a straight cut on the opposite side of the tree, almost to the wedge cut point.
Listen carefully to the warning sounds of creaks, groans or cracks, and move further away - the tree trunk will bounce back at the cut, sometimes in an unpredictable direction. (It could be coming at you and they are heavy!)