You can easily direct the light with an adjustable lamp and a mirror.
Eyeglasses can be used as converging lenses. (Page 5 of the book)
Look through the window. Now you can pick up the mirror in cellar 2 and put it on the desk. Adjust the lamp and the mirror up and down. Find the best position to direct the light onto the alarm keyboard in the neighboring room. This isn’t sufficient, however.
Read the reminder pinned to the wall and take the eyeglasses from the drawer. Use it on the mirror to focus the light on the alarm. Study the keyboard carefully. It gives a clue to the combination lock!