Xanathar's Guide, Mordekainen's Tome, other books

I might be missing it, but is there any way to import and or add these books to the compendium to expand out the reach of Monsters I can put into my game without having to look up their entire starts and/or own the book and copy over? Like, adding to the basic compendium the newer stuff that has come out? 

If you want the contents of  Mordekainen's Tome of Foes (for example) to be available in-game, you purchase it in the Marketplace . Once you have done that, the full contents, including Monsters, are available in any game you create. You can always see the contents, but if you want your players to have access to materials (Say, class options from Xanathar's ), you will need to turn on Compendium Sharing for that campaign. The number of slots and players available for sharing varies by subscription level.