Hello @LisaS60457 ,
The sign up form that's found in the View As Webpage / Share link is found in your Sign Up Forms tab, under the Basic Landing Pages section. If you need to edit it or look at the list(s) attached to it, simply click on the name of the Sign Up Form, make the edits, and save/finish the changes.
Any contacts that sign up this way will show as a sign up form or basic landing page-type sign up when looking at your contacts source. This won't apply to contacts that were already signed up with you via a different method, and simply re-signed up.