The email you signed up with can't be changed. You'll find it on the Account info page in your settings, where it's shown for reference but isn't editable — and there's no other route to changing it, including through support.
This is how the platform works today rather than something waiting to be built, so it's worth knowing what it means in practice:
Your email is how you sign in and how password recovery reaches you. Keep access to that mailbox.
If you've lost access to it, write to us at [email protected] and we'll talk through the options with you.
Everything else on your profile — name, username, bio, categories, links, photo — you can change yourself. See Editing Your Profile Details.
Need help? Contact support at [email protected]