Unzip the archive into the ship parts folder, leaving the folder structure intact. Set the set you want in the ship drawing program, and change the folder as required to access the extra accessories.
Hmm. OK, I don't have any "Ship Parts" folder. When I bought the game a few days ago, I must have gotten an older version. Hmm, yup, 1.21 and I see the current version is 1.33. Hmm, again. The update available is to 1.33.b1. Guess I"ll take what I can get..
OK, yay, it works! Pretty ship pictures are MINE!
-Bullethead NIHIL INIQVIVS QVAM ÆQVITATEM NIMIS INTENDERE