Actually the instructions are quite good, but you'll not learn how to use the editor by reading the instructions.

Your best bet is to edit an existing plane then try making SMALL modifications to the plane.

You'll find that you can adjust the C.G. in three axis manually.

However the correct way to adjust the C.G. is to change item weights or redistribute the weights of existing items as close to real world counterparts as possible.

That way the simulator correctly adjusts masses, etc for best realism.

"Moving" the C.G. manually fudges the results at best.

Changing the travel can be done via the beginner's interface, or you can go to the editor, click on the control surface to get to that "object" and adjust the travel in degrees. If you have the advanced editing functions turned on, you can also adjust travel up and down individually.

Expo is controlled in the "Input Channels" Software radio functions.

All of this is covered in more depth over at the Realflight forums. There are stickies there that deal with "Real World Physics Editing"... including screen shots.