To install, you first need to install the helper CGI onto your weathermap server, and make sure that it will have write permission to your weathermap configuration files. This script contains all the configuration, so you also need to edit it to tell it where your MRTG files live, and how to create URLs for them (14all or Routers2, etc) - or the same thing for Cacti if you use that. You also need to tell it if it can create Nagios Nodes (this requires you to install the Nagios datasource for Weathermap). Finally you need to set an application password.
Once this is working, you can install the Perl weatherman.pl on any client machine, and configure it to point to the helper CGI. Use 'File/Options' to set the URL, username and password (if any), temporary directory, and application password. Then it should work!
UNIX Systems, ITSS, University of Auckland, NZ
Woe unto them that rise up early in the morning... -- Isaiah 5:11