here are 2 options according to your experience level:

Beginner: Stretching Mio and sliding it down at the base of the penis, you can position the vibrating section upwards (toward the stomach) to stimulate her clitoris or downwards, when used in doggy-style, for enhancing his pleasure (the vibrations will stimulate the scrotum)

Advanced: Before the erection, place Mio at the base of the penis including the testicles, wearing a ring around the whole area makes him harder for longer by constricting a higher blood flow in the genital area. The erection is firmer than in the first option and the sensations around the scrotum and the perineum are a great addition to the overall experience.

Mio can also be placed at base of two fingers during foreplay for a more subtle, vibrating caress all over the body.