Jack's gone, for the weekend, so I will try to answer (Duskrider may explain it better)
If you already have the JPG, the text file calls on the picture, like a command, to open it, and place it on the Haptek Head.
Instead of having to type the command in the Haptek console, a text command, or a HAP file, with the command typed out, can be used to enter the command when dragging it into the Haptek console, or Haptek Window.
The command:
\settexture [figure=princess_girlShirt tex=[C:\Program Files\Haptek\player\data\standard\skins\GuitarShirt.jpg]]
Would swap the princess_girl shirt with the Guitarshirt.jpg
I hope you get my drift. I am not too savvy on commands, just copy and paste, lol.