I am a DM, and have a Master Subscription, and have purchased the Player's Guide.

All Players in my campaign should have the ability to pick subclasses from the player's guide when creating characters.

Players cannot access those subclasses from their account and there may be other content as well such as Backgrounds that is missing, but I haven't gone through everything yet.. 

Specifically, the Character Torjborn Svedish is in a campaign of mine, (Playername Smartalecpuppy) and cannot be set to a Tempest Cleric Domain.

Update: Found out that you have to click the "Enable Content Sharing" link on the campaign page.

Leaving this up as a testament to my stupidity, and in case someone else googles this issue and needs help finding a solution. :)