To change a user's email, you simply need to click on People then on Users, then click on the pencil icon beside the person you want to edit. You will be able to edit their email in the Email field. After you're done, hit Update User.

If you don't have this feature enabled on your platform, or if the Email field is not editable, you can simply send us a message letting us know by clicking Ask us a Question in the Help Resources window (found at the bottom-right corner of your page) and we'll enable it for you.