Can you point to a specific one? I'll try to give instructions based on that. (I noticed that the downloadable file for my submission has a different structure the other ones. I don't know why they didn't just make it all uniform.... maybe it is because they had to convert some from those who submitted a game-created faction, as opposed to an xml created one).
As an example, I looked at the Favixi by pendrokar.
In the zip there is a Favixi folder, then two zips inside. The one numbered 0000130 seems to be the "newer" of the two. Inside that zip are the folders that are relevant.
I created a folder in my mod folder called Favixi. Then I moved the folders inside 00000130.zip into the Favixi folder. And that should do it. When I start the game and select new game, the cute purple hamster is an option. (Unfortunately, for whatever reason, maybe something incompatible with Beta 6, if you chose the race and start a game, it crashes).