These instructions assume that you are using Tomcat, and that you already have Tomcat installed and running. If not, refer to Apache's website for Tomcat - http://tomcat.apache.org. If you are using an alternative servlet container, you will need to adapt what follows accordingly – consult the documentation for your servlet container for further details.
For a first-time installation:
When upgrading, be sure to make copies of your application-properties.xml and (if you have changed it) your strings.xml files. If not, these will be overwritten during the upgrade, and you will need to go through the configuration file editing process again. Once the new version of WLab has been installed, you can replace the stock copies of these files with your modified versions.