First of all, you have to set up an email account. There are plenty of free amazing ones around. I like Gmail, but that is just a personal preference. If you have one already, you determine what website it is, and go to it. On that website there will most likely be a login box (much like the one you had to use to sign in and ask this question) where you will type your screen name and password. 99% of the time you will be led directly to your inbox.