Adding/Changing Civics?

[Onionsoilder]

I was messing around the other day and I came up with a few new civics I would like to add into the game, but I am not sure exactly how. I checked the guides but either it wasn't in them, or I missed it.I have around three new civics for each category, so any help would be appreciated!

 

[Larklight]

I'd like to make some small changes to the final fronteir civics, so if anyone could answer I'd appreciate it too.

Edit: Maybe I ought to surf the site first.

Edit: Good job too, http://forums.civfanatics.com/showthread.php?t=138779 I think should explain it