HBO Max Purchase Over Internet

Sure. What streaming device are you using? You can simply download the HBO MAX application and sign in with your credentials. 

Basically, rather than going through DIRECTV, you subscribed to HBO MAX alone? That should not be a problem.

If you want to watch the HBO satellite channels, you need to cancel your HBO Max stand alone subscription and add HBO to your satellite package. You will then have access to the HBO satellite channels, HBO on demand through Directv as well as HBO Max streaming.

I really appreciate the quick and helpful responses, however, I don't think I stated the question correctly.  I have the DTV "choice" package (the cheapest they offer) so no premium channels.  However, when I turn on the TV I see many premium channels (Netflix, Hulu, Samsung Plus, etc.) available to me, and I did buy a Netflix subscription.  But HBOMax was not offered so I went to my desktop computer and purchased a subscription there.  I'm thinking that the only way I'll be able to watch it on my TV is connecting an ethernet cable between my WiFi router and the DTV box?  Thanks again.

No. Your DirecTV satellite DVR/Receiver has nothing to do with HBO Max streaming service. If your TV can't download the HBO Max App, then you'll need a separate streaming device, like Roku or FireStick.

There are 2 lower packages to Choice, Entertainment and the unadvertised Family.