Instructions
Open the "Dolphin" program on your PC and Select the "GCPad" option in the program's menu bar to open the GC Pad menu.
Select the button underneath the word "Device" in the GC Pad menu and select the "Mouse" option to open the configuration menu.
Select the button in the configuration menu that exists on the GameCube controller, then press the button on your mouse that you wish to correspond to the GameCube controller button. For example, select the "A" button in the configuration menu, then press the right mouse button to assign the "A" button functions to it.
Select the "OK" button when you have configured your mouse. Begin playing a game on your Dolphin, using your mouse as a GameCube controller.