Typically you don't have to do anything here, however if you wish, you may select terms to be assigned to imported records. This effectively adds a keyword to all entries being imported.
There are currently no "Term references" attached to the biblio node type. If you would like to associate a Taxonomy vocabulary with the Biblio node type, go the the admin/structure/types/manage/biblio/fields
page and add one or more "Term reference" fields.