My Computer is an icon on your desktop, double click on it.
Inside your main drive icon is "C".
Double click on that.
Look for a folder "Program Files".
Double click on that.
Look for a folder marked "Microsoft Games".
Double click on that.
Now you have a folder Flight Simulator.
Double click on that.
Laid out are all the simulator folders.
Aircraft is located in simobjects.
Follow the read-me that came with the aircraft.
You may have to put the contents of the downloaded effects into the effects folder, the same with the gauges-follow the read-me.