root@mybox:~/arc3# mzscheme -m -f as.scm
  -bash: /usr/bin/mzscheme: No such file or directory

http://download.plt-scheme.org/v372.html

The installer will ask you where you want to install mzscheme, you can choose any directory that is convenient for you. You do not need the option to create links in standard directories, say "no" to that.

Then you'd run mzscheme from the directory that you installed it to.

  ~/arc3$ ...where-you-said-to-install-mzscheme/bin/mzscheme -m -f as.scm

  * tried it with the absolute path
  * tried it without
  * tried running it in its directory
  * tried running it without parameters just to see what happens

  root@mybox:~/arc3# /root/mz/bin/mzscheme -m -f as.scm
  -bash: /root/mz/bin/mzscheme: No such file or directory
  root@mybox:~/arc3# cd /root/mz/bin/
  root@mybox:~/mz/bin# ls
  mzc  mzpp  mzscheme  mztext  pdf-slatex  planet  plt-web-server-text  setup-plt  slatex  swindle  tex2page
  root@mybox:~/mz/bin# ./mzscheme -m -f /root/arc3/ac.scm
  -bash: ./mzscheme: No such file or directory
  root@mybox:~/mz/bin#
  root@mybox:~# cd /root/plt/bin/
  root@mybox:~/plt/bin# ls
  drscheme   mred  mzpp      mztext      planet     plt-web-server       setup-plt  slideshow  tex2page
  help-desk  mzc   mzscheme  pdf-slatex  plt-games  plt-web- server-text  slatex     swindle
  root@mybox:~/plt/bin# ./mzscheme
  -bash: ./mzscheme: No such file or directory
  root@mybox:~/plt/bin# ./mzscheme -m -f /root/arc3/as.scm
  -bash: ./mzscheme: No such file or directory
  root@mybox:~/plt/bin#

You're going to need to get help on the PLT Scheme user mailing list for this one. (This is the first mailing list listed at the top of http://www.plt-scheme.org/community.html)

Tell them what operating system you're running, including the output of "uname -a", and which distribution of PLT Scheme you downloaded. Mention you need to run PLT Scheme version 372 specifically. No need to include the "-m" or "-f" options or to mention Arc, just show them the output of when you're in the bin directory and you type just "./mzscheme"

Then, once you have mzscheme working, we may be able to help with any Arc problems you have... :-)