To build a new .tarc file:

Run tarcbuilder.exe with the path to the contents, and the destination filename.

EX: 

   tarcbuilder.exe ./mygraphics graphics.tarc

The directory passed should contain the following subdirectories:

  graphics
  sprites
  textures
  hires

The PNG file contents of these folders will all be processed into the tarc file.
Any offsets included in the form of JSON files will also be applied.