You want to read SIPB's Inessential LaTeX document
(dvi,
postscript,
html). It's short but will give you a good
working knowledge of LaTeX. If you haven't used LaTeX much, you probably
want to print a copy of this; if your browser pops up a viewer for the
postscript you should be able to click a Print button on that, and if not
you can download the dvi and send it to the nearest printer with
dvips -h duplex iLaTeX.dvi
It's convenient to have a copy around.