Shalom,

The achemso package can be downloaded from:

http://www.ctan.org/tex-archive/help/Catalogue/entries/achemso.html

Please note that the natmove package is included. Also, jacsat.cfg is included
as I have already pointed out. Please read about installation and requirements
at: http://www.ctan.org/tex-archive/macros/latex/contrib/achemso/achemso.pdf

In addition, I am attaching the clevref.sty, xkeyval.sty and mhchem.sty
You should put them in a directory like:

TeXroot-dir/tex/latex/misc

Where TeXroot is your TeX-root directory. Alternately, you may want to put each
file in its separate subdirectory, like:

TeXroot-dir/tex/latex/mhchem/mhchem.sty

If you need additional macro packages, you can always download them from:
http://www.ctan.org/tex-archive/help/Catalogue/alpha.html

Afterward, you have to update the ls-R file. In the TeX installation on staff
server (tx), this is done by the file /usr/sharetexmf/web2c/mktexupd

You should look for a file named "TeXroot-dir/web2c/mktexupd", or, in its
absence, check which file updates the ls-R file.

Regards,
Irina