Though specific user instructions may vary, typically the creams should be applied to an already-erect penis. After waiting five to 10 minutes, you should take a tissue or washcloth and wipe away the excess before actually engaging in sex. Ideally, the sensation will be less intense, and you’ll last longer than you would otherwise.
The thing is, these products don’t “know” the difference between you and your partner and will work on any tissue it comes into contact with. Therefore, it’s especially important to wipe off any excess cream before commencing sexual activity so as to avoid transferring any of it to your partner, on whom it would have the same numbing effect.