Three options
If you want to have more than one message board, the first option is to have a Multiboard type message board script. Go download page. They are no more difficult than other DoubleMessageBoard to set up. The only disadvantage is that it is made for carefree management - it automatically deletes old articles above a certain limit and it does not come with one-click-archives.

If you want to have more than one "arch" DMB, you would like to have separate sub-directory for each of them. If you can not have sub-directories, then you need to have unique name for all files.

Before this page
See the advice for a novice first where you make compulsory changes on the first line (path) and the basic set up for password, url, etc. and, if necessary, "chdir" command to change the directory at the button of the basic set up. You may make any optional changes but please do so after you confirm that the default CGI works.

Separate sub-directories
If you can make sub-directories and if you can place the message board script bbs.cgi in each of sub-directories, you do not need to do anything special. Just let me remind you that you open bbs.cgi and change
################
# basic set up #
################
     :
     :
$html = "http://localhost/bbs.html";
to http://your web site/sub-dircetory name/bbs.html for each of them.

But if a cgi script works only in a particular directory such as /cgi-bin/, you need to give each message board script an unique name - such as Abbs.cgi for the message board in the sub-directory A, and Bbbs.cgi for the message board in B, and Cbbs.cgi for C, etc. And you change both
################
# basic set up #
################
     :
     :
$html = "http://localhost/bbs.html";
     :
     :
#chdir "/home/httpd/html/" or &error1("LINE-32",$erro5,$erro3,$!);
to
################
# basic set up #
################
     :
     :
$html = "http://your web site/A/bbs.html";
     :
     :
chdir "/your directory/A/" or &error1("LINE-32",$erro5,$erro3,$!);
for Abbs.cgi which is for the message board in the sub-directory A. And you do the same to Bbbs.cgi for B, etc.

Everything in one directory
If you want to put more than one message board in one directory, you need to have each of
################
# basic set up #
################
     :
     :
$html = "http://localhost/bbs.html";
$dfile = "data.txt";
$tfile = "temp.dat";
$arch = "A-";
unique. For example, you may have a message board Abbs.html and a corresponding script Abbs.cgi. And you change the scrpit Abbs.cgi to
################
# basic set up #
################
     :
     :
$html = "http://you web site/Abbs.html";
$dfile = "Adata.txt";
$tfile = "Atemp.dat";
$arch = "A-";
And for Bbbs.cgi
################
# basic set up #
################
     :
     :
$html = "http://you web site/Bbbs.html";
$dfile = "Bdata.txt";
$tfile = "Btemp.dat";
$arch = "B-";
etc. Now, the value of $arch is the prefix of an archive file name. You do not need to have them unique. Others must be unique else the scripts fall apart. To have an unique prefix for an archive page is for serviceability. It is easy to identify which archives belong to which message board.

Last, even if you need chdir uncommented, the value is the same as all message boards are in one directory now.
################
# basic set up #
################
     :
     :
chdir "/your directory/" or &error1("LINE-32",$erro5,$erro3,$!);