The package files ? You don't need to open them. Just copy into your mods folder. If they are rar files you need to donload 7zip or winrar.
I have a similar problem. I've downloaded CC (.package files) and put it into my mods folder and they never show up in my CAS. I saw in a tutorial I found that when you enter the game a box pops up to enable the cc in your game and I've never had that come up. I found the box when I was looking though options but it didn't seem to think there was any cc on my computer. The picture I included is the box I'm talking about.
Just in case anyone else has a similar problem, I figured out what was wrong. My resources.cfg file was blank so my boyfriend had to go in a physically write the code from somewhere he found online. I've included the code below in case anyone else has the same issue.
