Double-click on the Aircraft.cfg file you wish to edit. Select Notepad from the list of programs, click OK & it will open in Notepad. Alternatively right-click on the file & select Open With. This is explained in my Working with Windows article I mentioned in my earlier reply.
http://www.simviation.com/lair/windows.htm Please take time to read it along with my Windows Basics article.
Please back up any file you intend editing first. To back up any file right-click on it & select Copy from the drop-down menu. Then right-click anywhere in a clear space & select Paste. You will now have a copy of the file named Copy of Whatever in the same folder as the original. If anything goes wrong you can delete the edited version & rename the back-up copy to its original file name.