First, check to make sure you are using a version of ChemDraw that comes with this feature (eg. ChemDraw Professional or Chem(Bio)Draw Ultra).
You can determine the version of ChemDraw that is installed by going to the Help menu and choosing the About option.
Next, make sure ChemDraw is looking in the right location for the Structure to Name files. Go to the ChemDraw File menu and choose Preferences. Click on the Open/Save tab. Check the path of the ChemDraw Items folder listed in this dialog box to make sure it is pointing to the folder that belongs to the version of ChemDraw you are launching. Even if you believe it does, erase the path and reset it to the ChemDraw Items folder in the ChemDraw folder.
Last, you must select the structure using the marquee or the lasso tool first for the option to become available (when it appears grayed out).
If all these options check out and you still have the same problem, please follow this article to perform a clean installation of ChemDraw: