How do I change the email I sign in with?

For your security, you can’t change it yourself. If you own a workspace, contact support: we’ll send a link to your current address. If you’re a member of someone else’s workspace, ask its owner: they can send you the link from Settings → Members. Open the link, enter your new address, then confirm it from the new inbox. Your email doesn’t change until you do, and your password stays the same. To change your password, use Account settings.