NEED TO CHANGE EMAIL ADDRESS TO LOGIN!
I don’t know if you can do that. If there’s no post about that in the support section the ability might not exist. Our email is basically our username and I don’t know any website or game that allows the changing of a username.
Try posting in Players Helping Players or Account Issues, someone might have an idea there. Otherwise try emailing ANet to see what they can do. They might just send their emails to your new address but I doubt they’d be able to change the email (username) linked to your account.