I was having trouble getting my Windows (10 64 bit) PC to install the drivers for my ANT stick. This is supposed to be plug and play but not always so. Here is a link to a PDF with my solution. This link is temporary. I am trying to get Zwift to add it to their knowledge base. If you think they should, give them a little encouragement.
Installing a stubborn ANT+ Dongle on a PC (http://drive.google.com/open?id=0B1RQJI4Q6IHON0N5akFMYzYwNmM)
I hope this helps