Head to your Links dashboard and click the Link you want to change. Every part of your page is editable from there.
What you can change
Things that lock when a SubmitHub Ads campaign is live
If your Link is powering an active SubmitHub Ads campaign, a few fields get locked (title, pixel, URL slug) so the campaign doesn't break mid-run. Everything else stays editable. If you're running your own Meta ads on the side, nothing locks: those are yours to manage.