Are you able to power the units up? If so, entering the config mode is pretty easy -- that's covered in 34.2, Page 34-2 -- Press and hold the left most soft key and hold it while applying power.
From there spin the FMS over to the ENG menu, time settings is buried under there.
The Engine Time (Current Hours) can only be changed after unlocking the Engine Time Configuration
page by pressing softkeys 2, 3, and 4 in order, then using the FMS Joystick to highlight the Current Hours
The Total Time
(Current Hours) can only be changed after unlocking the Total Time Configuration page by pressing
softkeys 2, 3, and 4 in order (softkeys are numbered consecutively left-right, see Section 34.2), then using
the FMS Joystick to highlight the Current Hours field.