To update your own email address, see here:

http://support.wodup.com/en/articles/1208676-customize-your-profile-settings

If you're an admin and one of your members wants to change their address, they'll need to do that themselves if they've already started using their account. If you accidentally added a new member with the wrong address and you want to correct it, they you can do that from the Gym Admin > People screen in the Options menu.