The easiest way to develop Vaadin application with the NetBeans IDE is to use the Vaadin Plugin for NetBeans. It allows you to create new Vaadin projects easily and provides many features for working on a project. You can download the plugin at http://plugins.netbeans.org/plugin/50531/vaadin-plug-in-for-netbeans. The download page contains a link to a plugin features overview in NetBeans Wiki.

Without the plugin, you can most easily create a Vaadin project as a Maven project using a Vaadin archetype. You can also create a Vaadin project as a regular web application project, but it requires many manual steps to install all the Vaadin libraries, create the UI class, configure the servlet, create theme, and so on.