Check the OS version first, then upgrade if needed.
Then I would start with wiring the Octo directly up to a module, like the drumstation and maybe a synthesizer.
Then just put in a very simple sequence, don’t start writing a song first thing. Crack open the manual and start going through it page by page and actually perform the things described in the manual. You probably won’t get very far the first time through
You will probably want to skip over most of the advanced topics at first. Then I would start building a really simple song and reread sections of the manual as needed to complete the song.
Then hook the Octopus up to the rest of the studio.
At that point I reread the manual again, taking sticky notes and putting them on pages that had things I never tried to do. Then I set up a time to specific do the things I had marked even if I never had a use for them.
By this time you will be very fluent in "Octopus" and have it integrated well into the studio.
Things I think are most valuable to learn well are the EDIT mode for PAGES (to enter step pitch, velocity and length). TRACK multipliers and chaining, and dumping/saving the machine state.