Now save your copy . Quit ResEdit, and run the game. If it crashes it failed. If not, you succeeded. Patching using a DataFork Editor You don't need a special program to open a data fork.
Most text editors can do it.
But if you want to edit the file and save it, you need a special program. A good and free program is HexEdit. If you don't have it, you can downloading it from any Info-Mac archive. See Downloading HexEdit for information how to do that. First, make a copy of the program or file you want to patch.