I'm sorry, there's more than one way to skin a cat per say.
I'm not home so I can't say exactly what to do. Go to your username/saved games/ dcs world/ config/inputs/ copy and paste the Su25t
Rename the pasted file the name of the aircraft you want to fly.
Go into the file. There should be a LUA file called entry, or something like that.
Open the file with notepad++.
Replace the part that says Su25t with the aircraft you are trying to fly.
Open dcs world,go to options, and your aircraft should be in there.
The FC2 copy paste is not recommend. The way dcs world file is setup and FC2 is setup is off enough that it can crash with some buttons pressed.
you may have to repeat some steps into the program files/ dcs world/. I don't remember off the top of my head.