After you purchased the product, you should receive the license key through mail address that you provided in the registration process. To activate your product, it's better that you search for the registration key on your mail first. It's possible that the mail with the key to be stored in Spam, so you better check that folder too. If you didn't received the license key, you should immediately contact the developer on the official website. To be noticed that you will have to provide a proof of the purchase to obtain the license.