If you register as one of the other roles (EP, AEP, Author, or Certified Professional) you should have been provided a link and registration voucher.
Step 1. Follow the link and the steps below.
Step 2. Enter your details
Step 3. Enter your registration voucher
Step 4. You do not need to enter your billing address or payment information. This is not required.
Step 5. Scroll down to the bottom of the page. And press the button ‘Submit and check out >’.