You have installed the Navisworks Exporter for Revit, but it doesn't create the Add-Ins tab to add the tool. This seems to happen if the NW exporter is installed when no other add-ins are installed first. To resolve the issue you will need to take the following steps.
- Turn off firewall and virus protection
- Make sure you have opened Navisworks Manage and accepted the agreement.
- Install one of the other add ins (for example batch print)
- Reinstall the NW exported through the control panel...select the exporter, uninstall/change, reinstall
- Through the control panel, select the exporter again, uninstall/change, then add remove features, (don't change anything), select update then finish when it's done
- Open Revit to verify if the add in is now visible on the Add-ins tab, External Tools
- Turn firewall and virus protection back on.