Moving this discussion to the Dreamweaver support forum.
I'm not 100% on what you mean by "asset files".
You can download the entire DWCS6 here: http://prodesigntools.com/adobe-cs6-direct-download-links.html
Just make sure to follow the "Very Important Instructions" on that page or you won't get a download link.
Are you asking about the CS6 Online Tutorial Sample Files for first_website?
You'll need to extract the contents of this folder with either WinZip or StuffIt decompression utilities and save to your DW Local Site Folder.