Trimming is a way to stabilize your helicopter. If your helicopter rotates uncontrollably, you may need to utilize the trim button. If your helicopter over rotates clockwise (to the right), push and release the left side of the trim button until the turning stops. (Sometimes you need to click 15 to 30 time so proper flight is maintained )
If your helicopter over rotates counterclockwise (left) push and release the right side of the trim button in the same manner until the problem is resolve.