The old way to do this was to add a <Context ...> node to the <Host> element in the TOMCAT_INSTALL/conf/server.xml file.
More recently,
Tomcat has started to support 'context fragment' files.
These files are named after your context with a '.xml' extension.
For example, if your application is named myApp, then the fragment file would be named 'myApp.xml'.
In this file, put only the <Context ..> tag.
The file goes in the TOMCAT_INSTALL/conf/Catalina/localhost directory.
For information on the attributes of the context element, see this page:
http://tomcat.apache.org/tomcat-5.5-doc/config/context.html The docBase attribute is the one that allows you to tell Tomcat where you're keeping your applications files.
