From the login screen you can open a console using Ctrl+Alt+F1, log in and copy the file to a place where it can be accessed from a guest session (e.g. /var/tmp). Then you can return to the login screen with Ctrl+Alt+F7 and enter a guest session.
From the login screen you can open a console using Ctrl+Alt+F1, log in and copy the file to a place where it can be accessed from a guest session (e.g. /var/tmp). Then you can return to the login screen with Ctrl+Alt+F7 and enter a guest session.