Channels on AppleTV+
On my Mac and only Samsung TV that has AppleTV+ built in, I see other channels available like CBS All Access, Epix, HBO Now, etc.
I have been a subscriber to most, if not all of these since before the AppleTV+ Service was available. How do I sign into my account on the AppleTV+ App? I can only see where they want me to sign up. No area for "existing customer"
Thanks
QRQ60,