For example on a sun:

cd /
gzip -dc maxima-sun4-5.2-bin.tgz | tar xvf -

will unpack the binary in /usr/local

the Info files in usr/local/lib/maxima-5.2/info/maxima.info*
should be installed wherever you keep info files for emacs.

It is also possible to make an html version of the info, using
texi2html.