Using Resources

I can't seem to find an answer to this.  Odds are I'm looking in the wrong spot (as always).  If I purchase a book (ex: Xanathar's Guide To Everything ), do I need to be the GM to use the information like the subclasses, or can I use them as just a player?  If I can use them as just a player, can everyone in the current game use them as well? Reason I ask this is that a group of friends played for the last year on a campaign and I bought the person who's playing DM a book to make it easier to play the subclasses I wanted to play.  Now that that adventure has ended, another member of the group will be running a session and he doesn't have any of the books.  Just seeing if there's an easy solution.

My understanding is this: 1. Things you have purchased will show up for you in the compendium. 2.  You can't share your compendium unless you are the game creator.

Kraynic said: My understanding is this: 1. Things you have purchased will show up for you in the compendium. 2.  You can't share your compendium unless you are the game creator. 2a. Clarification: You can be the game creator and promote another player to be GM. The compendium will still be shared. Creator ≠ GM.