How Do I Pin "This PC" in Windows 8.1 ??
 

I'd also like to be able to add other folders to "This PC" ...if you have answers please do share.

Right click the desktop and go to Personalize and you will see options there on the left to adjust desktop icons. Pretty sure anyways.

Nope. I am trying to add folder to "This PC" formerly known as "Computer" or "My Computer"

As far as I'm aware you can't add folders to "This PC" and you couldn't add folders to "My Computer" either.

What you can do is create a folder elsewhere and simply make it a network share folder and map it. It then shows up in "This PC".