No, members should not register. Registration creates a non-member user account, and you should avoid having extra accounts. Please sign in with your membership number and surname when you are presented with a subscription request page like the following:
If your organization provides you with free access and you see a pop-up at the foot of the page advising you to register, just close the pop-up (e.g. by clicking "OK THANKS") and thereafter use your member's login of number and surname when you wish to sign in.