To be able to register or sign-up for the Customer Portal you first have to receive invitation. You'll get invitation from your Account Manager.

‌‌In the invitation email you'll get a description of the steps needed to successfully sign up and start using the Customer Portal. These steps are:

1. Open the Registration page by clicking the to it in the email. 
‌2. On this page you click the Register button. By this you accept the terms and policies that apply to the usage of the Customer Portal. Links to these terms and policies can be found in the invitation email.
‌3. After confirming registration you will be forwarded to a page where you can select identity provider such as Google or create your own.
‌a) Use other provider such as Google: After selecting the provider it will as for verification code, i.e. a code will be sent to the email registered for the provider (in case of Google it will be @gmail.com. Check you email for the code and copy/paste it into the Code field and click Verify. If successfully verified you are good to go and can click Continue to be forwarded to the Customer Portal.
‌b) Create your own user name and password. Click the Sign-up now link. You'll get a form where you have to provide minimal information about you and then select the user name (use on of your emails) and password (and confirm the password). Next you have to verify the email by sending verification code. Check you email for the code and copy/paste it into the Code field and click Verify. If successfully verified you are good to go and can click Continue to be forwarded to the Customer Portal.