If you like to give your subscribers the opportunity to update their subscription data you can simple add a {profile} tag in your newsletter campaigns.
If subscribers click the link they will get redirected to a subpage on your newsletter homepage. You have to define which form is used for the profile which allows you to increase or limit the fields subscribers can update by themselves
The link will look something like
http://yourdomain.tld/newsletter-signup/profile
You can change the “profile” slug on the Frontend settings page
For security reasons the link is only accessible after a click in the campaign or if the subscriber is logged in with the matching WordPress User account.
Please make sure you have setup your newsletter homepage correctly!