You can register a Cambridge GO account by following the link https://www.cambridge.org/go/signup/teacher/ for a Teacher account or https://www.cambridge.org/go/signup/student/ for a Student account.
Please note that for Elevate and Cambridge Learn Premium, you must have a book code to complete the process. This book code will be in the inside-front-cover of your print book if it was bought as a digital bundle, or it will have been emailed to you if you purchased a digital-only copy.