Intranet: means that URL you are registering is intranet URL, not internet (that it is on your private network), so it should be OFF for a regular website.
Theme: If you download Theme a place it on your website, you fill in "Theme" (finish the URL to Main.css file). If this is set correctly chat will be loading css definitions from your website.
Theme version: if you modify Theme files on your website, Theme version helps to force browser to reload new files (not use cache), so you simply start from 0 and after each change to files you should increase the number of version.
URL,
www.xxx.com is different from xxx.com, if you register
www.xxx.com then this is what you need to use when loading chat (it wont work if you load chat from xxx.com), you can either hardcode URL in api.blastchatc.php file under bc_getLiveSite function, or you can implement httpd url rewrite as described in this thread:
httpd rewrite instructions