You can personally edit your already linked Facebook account to another, via your account settings.

Make sure you are signed in to your preferred Facebook account via your Facebook app before proceeding.

1. Tap on  located in the bottom menu.
2. Tap on the 'EDIT' button next to the Facebook option.
 Settings > Profile
3. Press 'Continue' when you see the 'Covet Wants to Use to Sign In' pop-up.
4. Press 'Open' when you see the 'Open in Facebook?' pop-up.
5. Tap on your preferred Facebook account or press 'Log into another account.'
6. Press 'Continue' when you see the 'Log in With Facebook' screen with your profile picture.
7. Tap 'Yes' when you see the "Are you sure you want to link Facebook user [your name] to this Covet Fashion account?"
8. You will see your preferred Facebook account username under the Facebook option in settings, and you're done!