In newer versions of eclipse (I'm using 4.9.0) there is another, possibly easier, methods. As well as Project Facets, there are now Project Natures. Here the process is simple get the Project Natures property page up, and then click the Add... button. This will come up with possible natures included Java Nature and Eclipse Faceted Project Properties. Just add the Java Nature and ignore the various warning messages and your done.
This method might be better as you don't have to convert to Faceted form first. Furthermore Java was not offered in the add Facet menu.