Find out who has the book in their library (search all libraries rather than your own).
Check the TL list to see who to contact.
Email the TL with an ILL request including:
what the book is.
who they should sign it out to (Employee or student ID)
When the book arrives give it to the correct person.
When they are done with it discharge it and it will move to IN TRANSIT.
Send it in the inter-school mail back to the school in a routing envelope labeled with the school and teacher-librarian.