Well, it depends on the type of water purifier that you have. Most water filters just screw onto the faucet, but some models require permanent installation by a plumber. If you're not sure how to install it, your best bet is to call the manufacturer or take it to a local hardware store for assistance.

You can find water purifiers at most home improvement stores. They usually come with simple instructions for installation. However, if you're not comfortable installing it yourself, most stores offer installation services as well. Just be sure to call ahead and schedule an appointment.