HowTo on installing skins, scripts, etc?

I just spent an hour searching the forum, FAQs, stickies, and online manual... this is either buried VERY well or does not exist...

I'm a linux noob but I want to copy over my UserData, scripts, skins, etc but have no clue how... I only found XBMC under usr/share/xbmc and it will not allow me to copy it there.

How To anyone?

thx!