Just as you need to experiment with the different settings and features of your vibrator on your own, your partner will want/need to do the same.Allow him/her to test out the different settings, on a less sensitive body part before jumping straight to your sexual organs. Once you are both familiar with the different sensations of your toy can create, urge him/her slowly and carefully explore more erogenous zones. This is a fantastic exercise in communication, as you will need to let your partner know what feels good/better/best.
Treat this initial use as an adventure. Remember that practice makes perfect. A vibrator can also help create the multi-faceted pleasure many women crave, allowing for both clitoral and vaginal orgasms. During penetration, press the vibrator against your clitoris while your partner continues his/her thrusting motion. Or switch things up and insert the vibrator inside your vagina while your partner provides manual or oral stimulation to the clitoris.
Using a vibrator on him.
While a vibrator is stimulating when used on a man, it's much less than for women. He will probably want a faster speed from the start. A light touch is unlikely to be the best firmly pressing the vibrator to the penis will be more stimulating. Use a lubricant and focus on the head, especially the underside. Try moving the vibrator in small circles or in small back and forth strokes. You may or may not be able to cause him to climax with the vibrator alone. Try using it as a part of manual or oral play or as foreplay for intercourse. The other way to use the vibrator for his enjoyment is to have him watch you use it on yourself. Most men find this extremely arousing, and it can also be very instructive for them.