Both arms can be used for clitoral stimulation. The small arm is flexible with precision point vibrations, and the larger arm, whilst designed for internal use, can be used for broader sensations or a gentle back and forth movement on the clitoris. 

The larger arm will move against the g-spot. The g-spot is usually located about an inch or so inside the vaginal opening on the upper wall. Use some external + clitoral stimulation first before taking the g-spot dive. 

The flexible smaller arm can rest on the clitoris whilst the larger arm moves against the g-spot. This stimulates both the front and back of the clitoris (aka the g-spot!) for a powerful blended orgasm. 

The prostate is a gland located just below the bladder in cisgender men and people assigned male at birth. It is roughly the size of a walnut and is located about two inches inside the anus. The internal arm will move against this spot, and the flexible external arm can push back and rest against the perineum to stimulate the prostate from both sides.