First, a few prerequisites. You need an installed Java Development Kit (JDK) of version 1.4 or later. As of this writing, using GWT distribution gwt-mac-1.2.22, you cannot use the Java 5 features such as generics or autoboxing with your client-side code, but you can certainly use the Java 5 JDK compiler as you write these classes.
GWT 1.3 Release Candidate
The GWT developers released GWT Release Candidate (RC) 1.3 at the time we published this shortcut. This release is associated with the GWT open-source announcement, however, and did not provide any new functionality. The demo application was compiled and tested with gwt-mac-1.3.1 RC and the official gwt-mac-1.2.22 release.
You have to download and unpack the GWT framework. The download address is http://code.google.com/webtoolkit. You can download the framework for Windows, Linux, or Mac OS X.
The unpacked archive includes:
Documentation, including a Javadoc format for the GWT API classes;
The Java Archive (JAR) file (gwt-user.jar) containing the user interface classes and other parts of the GWT API (such as modules for handling JSON and XML formats, and making HTTP requests from your client code);
The JAR file (gwt-servlet.jar) that you can deploy to Tomcat or other servlet containers, and that includes the GWT API for the user-interface widgets and other objects. ...