If you had looked at the link I provided you would have seen the second selection on the menu on the left was
http://www.backtrack-linux.org/wiki/..._USB_Installer
which pretty much answers your first question.
The link I provided was simply the first page of Backtracks Wiki which covers everything from downloading, installing, usage, etc... . It seems pretty extensive, even more thorough than the documentation provided by many of the distributions with larger user bases.