You can offer subscriptions to a service in several ways, and give your visitors the ability to manage their subscription.
You can use Campaign to promote a service by:
Inserting a service subscription or unsubscription link into an email.
Inserting a link to a subscription or unsubscription landing page in an email. In this case, the service must be directly referenced in the related landing pages’ properties (see Linking a landing page to a service).
It is also important to give the subscribers the possibility of unsubscribing. To do this, insert a service Unsubscription link in the confirmation email (defined in the service properties) sent automatically to the new subscribers as well as in future newsletter emails.
Making a subscription or unsubscription landing page available on a website. The URLs that give you access to the landing page must specify parameters such as the associated service, as well as the profile ID accessing it. This ID can be defined in the landing page parameters (see Configuring a landing page).