The TADS website at www.tads.org has a small collection of "how to" articles about TADS 3 features. Most of the articles cover game programming and library feature topics, which, you've undoubtedly noticed, are almost entirely absent from the provisional TADS 3 documentation.
You can view the articles on-line on the TADS website, at http://www.tads.org/articles.htm. If you don't have a broadband Internet connection, you might find it more convenient to download local copies of the articles for off-line viewing. To do this, download the file http://www.tads.org/t3dl/t3_howto.zip, then unzip that file into your TADS 3 documentation directory (i.e., the same directory containing the very file you're viewing right now). The ZIP file contains a copy of "articles.htm" that you should use to replace the file you're currently viewing; the replacement is a table-of-contents file with hyperlinks to the individual articles.