You should first have your J2EE servlet container installed. The Tomcat servlet container is known to work well for Mapbuilder, as well as other related applications such as GeoServer.
Download the -war.zip archive and extract mapbuilder.war file to the tomcat webapps directory. Depending on your Tomcat setup, you may or may not have to restart Tomcat. The default tomcat installation will expand the .war file automatically. Installation details for other servlet containers may vary.
The required server side scripts are automatically available as servlets, and configured in /mapbuilder/WEB-INF/web.xml. By default, these are: /mapbuilder/proxy for the proxyUrl and /mapbuilder/writeXml for the serializeUrl config property. If you install Mpabuilder using a different context name, it will be automatically detected.
Other aspects of the Tomcat setup (where $catalina_home refers to you base directory for the servlet container):
The server scripts use the Log4J logging package which is configured by the file $catalina_home/webapps/mapbuilder/WEB-INF/classes/log4j.properties. By default, logging level is set to INFO and by default there will be a log file at $catalina_home/logs/mapbuilder-log4j.log. Please refer to Log4J documentation for more details on how to configure the logging facility.
File save directory:
The file save directory is where files are written to disk by the serialize script. This directory has to be writable by the web user and it is up to the application to purge it. The location of the directory is configured in the Mapbuilder context deployment decriptor at $catalina_home/webapps/mapbuilder/WEB-INF/web.xml and defaults to $catalina_home/webapps/mapbuilder/temp.