Instructions
Plug your controller into one of the free USB slots on your PC. Wait for Windows to configure the controller.
Launch your SNES emulator.
Open the settings to modify input devices within the emulator. This will be accessible from the emulator's main "Config" or "Settings" menu.
Click the "Set Keys" or "Set All" button. When prompted, press the buttons on your controller that you want to correspond to the SNES buttons in the prompt.
Save the settings if they do not save automatically.