Now that an SDK and portal server have been configured you can create a new Liferay plug-in project. Go to File > New Project... > Liferay > Liferay Plug-in Project.
In the Liferay project wizard page, the newly configured SDK and Liferay Runtime should be pre-selected. Also the plugin type "portlet" is the default. Simply type in a project name and corresponding display name and click Finish.
If it worked you should see a new plugin project in the package explorer.