Toshiba e-STUDIO3510c Operator's Manual page 217

3
Key in the password (5 digits) for the selected box, and then press
the [ENTER] button.
If no password was set when the box was created, skip to step 4.
4
"Are you sure you want to delete this box?" appears. Press the
[Yes] button to delete the box.
The box is deleted.
Deleting User Boxes 215