Download and some env configure
?1. download gwt version gwt-windows-1.4.60 from http://code.google.com/webtoolkit
?2. unzip gwt-windows-1.4.60.zip file
?3. set system env variable GWT_HOME to the path where you hold your gwt files
?4. add %GWT_HOME% to your env path

Google Code Home > Google Web Toolkit > Getting Started Guide , it's a good place to get start.
You could follow this guide and get a first impression of what GWT can do and how convenient it is.

Usage
projectCreator -eclipse MyProject
ApplicationCreator [-eclipse projectName] [-out dir] [-overwrite] [-ignore] className

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Eclipse plugin

cypal.studio.for.gwt
?1. download from http://code.google.com/p/cypal-studio/ version: cypal.studio.for.gwt-RC2.zip
?2. install this eclipse plugin (install it by new local site or just copy files, it's up on you )
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GWT Designer?

?1. download from http://www.instantiations.com/gwtdesigner/index.html
?2. during install you need to choose Eclipse base location and GWT_HOME location
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?Study how to use this plugin,
Webdemos
http://www.instantiations.com/gwtdesigner/demos.html

GWT desinger document homePage
http://downloads.instantiations.com/DesignerDoc/integration/latest/docs/html/gwt/index.html

Tutorial: Creating a Login application
http://downloads.instantiations.com/DesignerDoc/integration/latest/docs/html/gwt/tutorial/tutorial_login.html
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