If you want to distribute the logins on your own, if you want only certain users to register, then you can deactivate the link "Sign up now", so only users, who have a login already, can log in: Tools & Administration > Portal Settings > Login & Password > Allow self-enrollment.

In this case you have to distinguish between not registered users reading the story ("Please registrate here") and users who are already logged in ("Please update your profile"). That's why you can solve this only with Design Attributes:

1. Create a Design Attribute and use the placeholders $linkRegistration and $linkRegistration:ID (take a look at the Placeholders below the field Code).
2. Then use this Design Attribute in a Story.

If you want to use this issue in a campaign you have to create a shortcut which links to that story. You cannot use the given placeholders in a campaign.

Registration profiles are different kinds of profiles containing forms e.g. for registration of new members, member profiles or when portal masters add a new user.