Applicant's have the ability to update their own user profile by clicking My Profile on the left side of their public submission portal. The one field they cannot edit is their email address. As an admin, you have full access over their user profile including updating their email address.
To update an applicant's user profile, click Applicants and then Search on the left side navigation.
Search for an applicant by typing into the search fields or leave them blank to show all applicants.
Click Select on the applicant you want to manage.
Here you can update their profile and make any other edits as needed.