You must change the application.name in your build.xml found the workspace-ui project as Diana mentions. In addition, I assume you want to change the URL that your EAR is deployed to?
If so, you need to change the web.xml file found in the templates folder in the workspace-ui project. In addition, in the LiveCycle Administration Console, you must register the new URL in the config.xml file. Instructions for both are found here on pages 29 and 35 respectively. Hope that helps!