Emulator game controls and config

[ALF]

I have fceu emulator for NES.
How can I change the control buttons?
ALT button brings on menu, jump, and enter. Three functions on the ALT button.

[hagbard]

Start FCE Ultra, then menu "Config" -> "Input", select "Gamepad", click on "Configure", then click the key you want to remap and press the button/key you prefer for each button/direction