Hi,
2 ways of doing it, but certain of one
Go to your controls assignments in FS 2004, select control you want to assign to your stick, once pop up tells you to press the button to assign control press button you want on the stick.
Second method would be using programming software which might be available for your stick, i know that thrustmaster has best software available, but i am not sure if it applies to your stick. Check at the link below if there software and download manual too
http://ts.thrustmaster.com/eng/index.php?pg=files_faqTake care