How to subscribe to Paramount Plus?

​​My parent has Directv (streaming) Ultimate, with 140 channels, and would like to subscribe to Starz, Peacock, Paramount Plus, Discovery Plus and AMC Plus.  ​​

​​I don't have a TV and have no clue how to do this, and at work, the IT staff always sets up TVs, so I'm clueless (and frustrated).  I've logged into Directv online.​​

I added Starz, Discovery Plus and AMC Plus and Peacock (online), but I don't see Paramount Plus.

​​Could anyone please tell me exactly how to do this?  And do I do it online or on the TV?​​

​​Thanks!​​