This week's book giveaway is in the OCPJP forum. We're giving away four copies of OCA/OCP Java SE 7 Programmer I & II Study Guide and have Kathy Sierra & Bert Bates on-line! See this thread for details.
Create a run configuration for the project. (right-click the project, Runs As | Run Configurations). In the Run Configurations dialog create a new Java Application and specify the Main Class on the ?Main" tab in the dialog.