Is there a tivo for dummies?

Hiya,

I'm a rank n00b. I once had a directv tivo and loved it, but this is an entirely different kettle'o'fish.

I got my tivo roamio OTA yesterday and I have it all hooked up, but I am clueless as to what all the different options are and do.

F'instance: when I create a onepass, it shows me all the previous seasons' episodes. Sometimes they are playable and sometimes not. I get it that they are not always available, but why does it show me the ones that are not available?

I currently have uverse which doesn't work with tivo. That's ok, I'm trying to cut the cord. I subscribe to HBO on uverse, yet it won't let me add HBOGO to my channels (or whatever that is) on the tivo. I can get there using my roku and Amazon, though. Why would that be?

Why oh why is there no user's manual - online or otherwise. There are so many options that I have no idea about. Is it all supposed to be eminintly obvious, because I can assert that it isn't.

Any and all suggestions about sources would be welcomed.:confused:

Z.
SoFL