It's all explained in the manual, and quite extensively so, it's not possible to repeat on the forum what is already explained in the manual.
If, after reading the manual, there's something you don't understand, then please specify what exactly you haven't understood in the manual.
The GSX manual can be accessed in one of the following ways:
1) From the Addon Manager menu inside FSX, selecting GSX and pressing the “Open Manual” button
OR
2) From the Windows Start button, under the FSDreamteam program group, there’s a link to the manual
OR
3) By browsing your Add-on Manager\fsdreamteam\Couatl\GSX folder, the PDF manual is there.