As shown on the picture above click on the drop down menu and select New Project. This will open a new window, where you have to scroll down and select Web Project as shown on the screen bellow:
On the Page Flow Technologies, just select None and click on next.
We do not need to include any special libraries here inside so ignore this step as well and click on next.
Click then on next and then on finish to complete with the creation. Now we do have a project folder which looks like this:
Having this we can copy our GWT project into here. Just get the folder where you create previously your GWT project and copy the content of the otn folder inside the JDeveloper Otn project folder. Now your project will look like this:
Using the build-in Ant support in JDeveloper you can build and run your GWT application now.
In the next weeks I would try to research about how to configure the GWT applications to able to launch it directly from the JDeveloper. Using the knowledge about you can for example star and build portlets for WebCenter Portal using as UI the GWT Framework. I would try to follow this article and show you how to this.
You can also find the project I created above here.