Ordinarily you would have Inernet service to your house with a WiFi router, and you would connect through your router.
The fact that you are asking the question leads me to believe that you are not paying for Internet service and think that WiFi is just available out there.
That used to be the case, but nowadays most of your neighbors probably have their routers locked down with a password.
I’m connecting to the I-net via Verizon FIOS using their router, which does have wireless capability but my computer is connected via a physical line. But, I can plug the Kindle into a USB port on my computer and download via this connection. Is that correct?