Nikon D300 Complete Manual page 222

7. Use the Direction pad keys to navigate to the SETUP
menu (wrench icon tab).
8. Use the Direction pad keys to navigate to Firmware
version.
9. Press the > key on the Direction pad to display the
firmware version.
10. Navigate to Update and press the > key on the
Direction pad to get to the update dialog.
a. Use the Direction pad to navigate to Yes.
Thom Hogan's Complete Guide to the Nikon D300
V1.02
Page 222