Visit YaBB! YaBB 2 Quick Installation Guide - Installation 1
Please note that wherever 'YaBB.pl' is referred to, you may have the 'YaBB.cgi' file instead. They are the same file with a different name, depending on which package you have downloaded.
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First open 'AdminIndex.pl', 'Setup.pl' and 'YaBB.pl,' which are in the 'cgi-bin/yabb2' folder of the package you downloaded. These files contains a path to your server's Perl location. Generally, this setting is correct, but Perl can be installed in different locations. For example on a Windows or WinNT host, your Perl path should probably be set to #!C:/Perl/Bin. On a Linux host, the path is usually #!/usr/bin/perl. Check your server for the proper path and change accordingly.

Next open 'Settings.pl' and set the variables inside as follows:

$mbname
The name of your YaBB forum
$cookieusername
Name of the username cookie (no change necessary)
$cookiepassword
Name of the password cookie (no change necessary)
$mailprog
Location of your sendmail program (generally "/usr/sbin/sendmail" or similar)
$webmaster_email
Your e-mail address, such as qq~webmaster@mysite.com~;

The remaining settings in Settings.pl are not required, but are only feature and layout variables. It is recommended that you DO NOT change them until you get YaBB working! After that, have fun....