I assume you found an upgrade file in which the setup sheet and functions sheet were already correct for the device you want to control (except maybe you needed to change the model of JP1 remote selected on the setup sheet).

Rearranging the button assignments is done on the Buttons sheet.

For each button named in Cols A/B you can click in col C to enable a drop down menu to select the function you want assigned to that button.

But the rows that are greyed out are not available at all and the rows that start with @ won't work if you're doing a simple upgrade by .wav file (they can be made to work if you're replacing the entire eeprom contents by .wav file or JP1 cable).