The details for setting you your server so that you can get it to re-read the configuration files, look at and manage the LAS cache and do other tasks is described in the adminstration guide.
If the only changes you make is to the files contained $TOMCAT_HOME/content/las/conf/server the re-initialization tool in the admin interface will do the job, but if that's not set up just restarting the Tomcat server will have the same affect.
If you've made changes to the Java source or some parts of the WebContent directory, you need to rebuild the war file and copy it over to the webapps directory of the Tomcat server. The "ant deploy" command run from the command line in $LAS_HOME will do the job for you. You may need to restart your server to see the changes take affect. Check your server log to see if the server successfully reloaded the changes or needs to be restarted. The safe bet is to restart your server.