Select File > New > Other... > Plug-in Development > Feature Project**, and choose the plug-ins you want to add.**
One important caveat is that in order for features to be installable using an update site, you have to specify a license agreement. Open the Feature Editor on your feature.xml file, select the Information tab, and enter the license text under the License Agreement section. For testing, a simple CPL 1.0 will do.
Q: How do you know if your project is a "Feature Project"? A: (I'm guessing) It has a feature.xml