Easiest way for me to add a new repaint is to create a folder in the aircraft the repaint is for and call it something that I know it is. For example:
Texture.united, or Texture.N4381F, etc.
Then open the aircraft.cfg file with notepad and copy the last [fltsim.x] entry. For example if you have 3 repaints already installed, it would be [fltsim.3]. Copy the entire entry as shown in MattNW thread.
Then paste this entry below the one you copied. All you have to do now is rename the [fltsim.x] to the next consecutive number, make the title=a unique name, different from the rest, the texture=the name of the texture file minus the word texture, the atc_id=the tail number of the aircraft repaint, and the ui_variation= a unique name of the repaint different from the others in this aircraft folder.

Once you do it a few times it becomes very easy....
