Dash 8

How do I go about making a seperate texture file for the left side of the Dash 8 that comes with the Pro ed. I have messed around with it for so long,,,,just can't figure the thing out.
Flight Simulator and other chat
https://forums.simviation.com/phpBB3/
https://forums.simviation.com/phpBB3/viewtopic.php?f=13&t=31695
Thanks for the help >:( >:(
I have looked at the tutorials, can't find anything, maybe I'm looking at the wrong one.