Hallmark Movies Now App

We already have a subscription to the Hallmark Movies Now (HMN) that was created outside of the Xfinity service. I'm trying to access that using the Xfinity HMN app through our cable box but the app doesn't allow me to log in to my current account. It only asks for me to create an account and it will charge me $5.99 a month. We're already paying for the service. How do we access our existing account without paying twice?!?