Even though Navisworks 2014 will allow you to open a Revit file without having first exported the NWC file from Revit, there are times when you still need to export from Revit, depending on workflow and file management practices that you may have at your firm. If that's the case, you can download the Navisworks file exporters (which include Revit 2014) from here: http://www.autodesk.com/products/autodesk-navisworks-family/autodesk-navisworks-nwc-export-utility
However, simply installing the exporters is not enough to make them work.
After you install the exporters and launch Revit, they won't be displayed on the Add-In's tab of the ribbon as they should be. To fix, make sure that Revit is not running, then go to Control Panel - Add/Remove Programs. Select the Navisworks Exporters from the list of installed programs and select "Uninstall/Change". When the maintenance dialog appears, choose the option to "Add/Remove Features". Make sure Revit 2014 is checked ON (it should be, and it was probably checked on when you installed in the first place). Click on "Update". It should only take a minute or two, and when it's done, you should be able to launch Revit 2014 and see an "External Tools" item on the "Add-Ins" tab of the ribbon, which will include the Navisworks Exporter.