Install the plugin into 7.3 and then you're able to create new Play projects via the New Project dialog or open any existing Play project, such as the sample applications in the Play distro:
This is how opened Play projects look like in the IDE:
The sources of the plugin (in the form of a Maven module) are available here:
Do you want to contribute to this plugin? You are MORE than welcome to do so, please leave a message here either with your ideas or with your username on java.net so that you can be added as a committer to the project.