This is my preferred way of installing files but you use any method that you like. I use Windows Explorer.
1) Make a folder called "Temp" or "Crud" or anything you like in the root directory of Windows Explorer.
2) Unzip all the files and folders from the downloaded "su_31fsx.zip" file to the folder you just made (for example "Temp").
3) Select the folder called "Sukhoi_SU_31" and hit "ctrl-c" to copy the entire folder and its contents.
4) Go to the "c:\Program Files\Microsoft Games\Microsoft Flight Simulator X\SimObjects\airplanes" folder of your FSX flight simulator and paste (ctrl-v) the copied "Sukhoi_SU_31" folder there.
5) Be sure to read the "READ_ME.txt" file in the "Temp" folder. That is it. If you wish you can delete your "Temp" folder now but I would save the downloaded "su_31fsx.zip" file somewhere just in case of emergencies.
