To edit a person on a list, hit the three dots to the left of the x and hit "edit."
Editing someone here also updates their information everywhere they appear — on other sessions and on your People pages.
Related articles that might be helpful:
Start with the guide to lists on schedule items
See how you can attach people to schedule items
See how you can remove a person attached to a schedule item
If you have a lot of information to enter, you might consider using our Import from CSV tool.