After unzipping the editor, double click the field deditor icon to open a diagram of the playing field with numbers on it. These are the hex numbers which show the field positions in c2k2.
Click on open, and in the box that appears go to your c2k2 folder/data/editor then one day or test. Then open the folder which you wish to amend and you'll see 15 cfg files. Double click on one , then click on 'view your field' to see the fielding positions.
Then click on 'back' and amend the field positions by entering the equivalent hex number on the diagram in one of the boxes on the right hand side.
Keep clicking 'save' and 'view your field' to see the fielding changes you've made.
Hope that makes sense!