Hi From the Firefox for Android home screen, select the three lines icon, followed by Settings. Choose Firefox Account, then your email address at the top of the screen. A webpage will load that will allow you to add a seconday email. Once added, you can change this setting to make it your primary account email address. From a desktop copy of Firefox, this [https://support.mozilla.org/en-US/kb/change-primary-email-address-firefox-accounts article] will help.