Open TOOLS Ribbon-Tab and find SimLab FBX Exporter section as shown in the image below
Click on Settings to open the settings panel that contains export settings and licensing information. Activating and getting a trial license can also be done from this panel.
If the plugin doesn't work correctly, chack your DWF export settings in inventor. From Inventor menu go to Export > Export to DWF, the Publish Assembly dialog will open. Change the publish option to Express, and make sure that the settings checked / unchecked, as shown in the image.