FS has some default mappings for the Yoke USB. They're defined in a file called "Devices.cfg" that should be in your FS folder. If you just plug the yoke in and use it with the default Windows drivers, those are the ones that will be in effect. You can also see them by getting to the Controls Assignment dialog in Flight Simulator and looking through the list of axes and buttons. You can manually change the assignments there.If you want to create a map to do anything beyond that, you'll need the CH Control Manager. Don't use the one from the disk, download V2.20 from their website. It can be a little chaotic at first, though, because of the way FS handles the Yoke USB vs the way it handles the "Control Manager Devices" that the software creates. There's a freeware utility and documentation, CMFS, available on my website that explains what happens and has some examples. It was written for FS2002, but it's all generally the same deal for FS2004. You might want to have a look if you're going to try the Control Manager.
Hope this helps!
- Bob
The StickWorks
http://www.stickworks.com