Hi Kim Kha,
It's hard to provide support for the problem you're experiencing without more detail. It seems like you're just getting started with GWT and having some trouble getting used to some of the core concepts on setting up and creating a GWT project.
I would strongly recommend checking out our Getting Started guide and seeing if that helps get you up and running with GWT. If not, you can post back on the group and mention which step you're getting stuck on so we can provide more focused support.
You can check out the getting started guide at the link below:
Once you've completed that, you might want to take a look at our new tutorial which walks you through building an actual GWT StockWatcher application from start to finish.
You can check out the tutorial at the link below:
Hope that helps,
-Sumit Chandel