Hi there @KiwiCat,
Welcome to the Community! I’m glad to see you are starting off with Klaviyo and found the Community to ask your great question in.
The unsubscribe link you've inserted in your email templates may not be getting recognized by Klaviyo if it isn't in the proper format. If Klaviyo doesn't detect a suitable unsubscribe link at send time, one will be automatically inserted. To prevent this from occurring, you'll want to make sure the unsubscribe link included in your emails includes the correct tags found in this guide:
How to Add an Unsubscribe Link to Klaviyo Emails as well as a related guide here.
It's also important to note that a real unsubscribe link will not populate when Preview Testing, only a Placeholder. If you're seeing the Placeholder page come up, that indicates the link is formatted correctly and a true Unsubscribe page will appear during a live send. When sending a preview email, it is expected behavior for the unsubscribe/any template syntax links to lead to a 'placeholder page' - this actually means the link is working correctly. As of now, the only way to select the unsubscribe link and be led to the real unsubscribe page is to actually send an email rather than sending a preview. More information on previewing emails can be found here!
If there is a placeholder text within your unsubscribe link, you would just need to reformat it so it is just {% unsubscribe %}.
Hope this helped!
Alex