John, I gather that this voting business is, like marriage, a two-part invention.
First, you register
here by June 8.
Once The Powers That Be sniff you out (via the aforementioned registration process) to determine that you have the necessary credentials for enfranchisement, they instruct you on how to actually cast a ballot, either online or in person. That's Step Two, and it will only go on between May 22 and June 17.