All you gotta do is download them. Unzip them to your Mods folder. For vista its here: C:\Users\'YourUsername"\AppData\Local\Ironclad Games\Sins of a Solar Empire\Mods
Then Start up the game. Under the Settings tab, there is another tab called Mods. Just click on that and it will bring up the mods you have put into your mods folder. Select the mod you want to enable and then click enable mod.
Just like that your mod is ready to go.