To get the integration working, you need to register the 32-bit Excel integration following the instructions in this article.
After you have done that, you need to register the 64-bit Excel integration. This is done the same as the 32-bit, except that you replace the 32-bit DLL files with 64-bit ones (available as an attachment at the bottom of this article). The integration should now be working.
64-bit Excel Integration Zip link: