Add a bibliography : click on the menu "Publications / Add a list" and select the file : Projects/Tutorial/Hitchcock/Hitchcock.pbl. 

A complex dialog shows the imported publications. Close it ("Ok" button).

Click on the root idea ("Alfred Hitchcock"), display its properties and click on "Associations" tab. 

In the "Publication" area, add a book by clicking on the "Add" button, and, in subsequent dialog, select François Truffaut's book. 

Validate all dialogs.

A bibliography reference has been added to current idea (use preview to check).

Press Ctrl + Shift + E to update the indexes and click on the "Bibliography" link (page bottom) to see the bibliography you have imported.