Click on the relevant column and press F2, then you will have the opportunity to change the content.
For example. if you want to change an existing code, go to the Codes setup window and click once on the Code you want to change and tap F2 on your keyboard.
In the above example, you want to change code 1 to LO. Tap on code 1 and then tap F2 and type in LO and press Enter to finish and the change will be made. All entries previously made as 1 will now show as LO in the data entry windows.
It is only in the data entry windows in the "General"-menu you are able to press F2 to edit a grey column.