Use your word processor tricks to select more than 1 reference:
Hold down the Shift key and drag to choose several references
Hold down the CTRL key and to highlight several references, not near each other.
The left pane of the library window lists groups of saved references. These groups are used to organize the references in your library.
Imported References = a temporary group that is replaced each time you import (but remain in the Library)
Configure Sync.... = Syncronizes your desktop and online library
Unfiled = references that are in your Library, but not part of a group
Trash = references that have been deleted from your Library, but are still retrievable until you empty the Trash