You will need the amazon appstore store installed and the app must be purchased

I was not allowed to purchase the app from the Amazon app store on my Xoom - but I found that I could go to the App Store on my PC and purchase it, even though it was incompatible with all my registered devices. After that, I could get HBO GO (which I had installed from the apk - thank you for the link) to run without telling me I didn't own the app, could buy it, and had no right to download content.