To register for a Terra account, you will need a Gmail account (or an institutional email account associated with a Google identity). To register for a Gmail account, visit the Google sign-up page. Once you have a gmail account, you can go to the Terra log in page and click the option to "sign in with Google". When you sign in for the first time, you will be asked to confirm some information and to accept the Terra terms of service. Once you do, you're registered!