Here's PRE-Flight configuration manual for milehighwings.com USB interfaces:
http://www.milehighwings.com/manual_usb.htm#PRE-Flight
RealFlight's controller should be configured similarly.

A word of caution: only up to version 1.95 freeware PRE-Flight allowed to use all joystick axes. The later free versions limit your controls to only two axes--in order to use all four axes, you have to buy a paid version.

Boris