Open Firefox and make sure you are signed into Sync (click the menu button new fx menu and look for your email address instead of "Sign in to Sync").
   Go to https://accounts.firefox.com/settings?canChangeEmail=true. Visiting this special URL will make the feature visible.
   Under Secondary email, add another email address and click the Add button.
   Follow the instructions in your verification email to confirm your second email address.
   The Make primary button will now show up under Secondary email. Click the button to change this to your primary email address.

   make primary

THE FOLLOWING DID NOT WORK BECAUSE NO FX MENU APPEARED Change primary email address on Firefox Accounts Firefox Accounts now lets you change your primary email address. The feature is still under development and is not available by default, but you can follow these steps to enable early access. Open Firefox and make sure you are signed into Sync (click the menu button new fx menu and look for your email address instead of "Sign in to Sync"). Go to https://accounts.firefox.com/settings?canChangeEmail=true. Visiting this special URL will make the feature visible. Under Secondary email, add another email address and click the Add button. Follow the instructions in your verification email to confirm your second email address. The Make primary button will now show up under Secondary email. Click the button to change this to your primary email address. make primary