[anita sancha]"now I am even more confused than ever. 10.1 seems to have no way to collect all the files I have used...... "
You select the Project or Projects you want to archive in the Browser.
You then choose file > Copy to Library (or Move to Library) > New Library.
Copy will copy media, move will move material out of the current Library.
Name and save the New Library to your archive location.
FCPX will ask if you want to include optimized or Proxy media, you can choose if you'd like to keep this media or not.
Then once FCPX is done saving, you select the new Library and choose File > Consolidate Files and choose to either consolidate the media directly in to the new Library you just created, or into a folder next to the Library in your archive location.