There is no way to convert project files externally. Those files would have to be saved back to CS6 from a CC.
Without spending some money, nothing. After Effects is not backwards compatiable, you cannot open a CC project in CS6 unless you open it in CC and save is AS as CS6 file. There is a program that will let you do that, however, it costs some money and I don't remember what it is called. You should be able to google it though.
I reccoment learning from this site: videocopilot.net, starting here: http://www.videocopilot.net/basic/
The basic training is a little old, but what you learn there is the same in newer versions. There are a ton of tutorials on the main website and it is where I learned almost everything I know. They also have some nice plugins.
I recommend against starting with the Video Copilot basic training. It is now far enough out of date that it is no longer a good place to start.
Start here to learn After Effects: