Spermicides are an add-on option and not very effective on their own. As such, they should not be used alone as a contraceptive. However, when used with a diaphragm, a cervical cap or a condom, they suddenly start making an impact. Spermicides come in many forms: pastes, foams, films, and more. They work by creating an environment that makes it difficult for sperm to move around freely.
As spermicides aren’t recommended as a contraceptive on their own, the instructions on how to use them lie in the other contraception method you are using them with. You need to put spermicide into the vagina 5 to 90 minutes before you have sex. Generally, you need to leave it in place at least 6 to 8 hours after sex. You should not douche or rinse your vagina during this period. Instructions can differ for each type of spermicide. Regardless of what contraception you use them with, remember to pay attention to expiry dates.