Thank you for reaching out to the Community! You will first want to edit the signup form or event that the list is attached to and make sure it is attached to another list instead so you can delete the old one. Thanks!
Thanks. Yes, I did see that solution come up when I tried to delete my contact list, but it wasn't clear really how to do this. What I figured out was that I had to go in to the design of the landing page and delete the registration button. That is the only way I could find to detach the form.