Extract these files into your /Freespace/Data directory and all should be well.
If that doesn't work, here's a list of files and where they should go:

comp.zip - freespace\data\missions
competition.txt - freespace\data (this can go anywhere you want)
commandbrief.pcx - freespace\data\interface
loadingbg.pcx - freespace\data\maps

When you're done, simply delete the .pcx files to return to normal freespace artwork.

Enjoy!