Go to aces high home webpage
http://www.flyaceshigh.comOn the left side of the screen select Help, Game Controls, Joystick Selection. When that's done select Mapping Joystick Buttons.
Hopefully that's what you need. If its more technical make sure to check your joysticks connection (USB's especially can be sloppy connections) and make sure you visit the sticks manufacturers homepage for updated drivers and help forums.
If that don't do it. Come back here and post again. Let us know the kind of stick you got and anything else that may help solve the problem. Somebody will be able to get it figured out (hopefully).
Best of luck.