If you are trying to connect MyFitnessPal to Heads Up Health you will need a MyFitnessPal username and password. FaceBook login will not work in this scenario.
To obtain your MyFitnessPal username and password:
Disconnect the link between Facebook and MyFitnessPal. MyFitnessPal will then prompt you to create a dedicated password.
If you require Facebook integration to remain on, you can click on the MyFitnessPal "Forgot my password" link on their login page. You can then reset your password and use it to connect MyFitnessPal to Heads Up Health.