The details are posted on the
member website, or right here:
Members with Disney Resort hotel reservations during the event can register online beginning Wednesday, June 6, 2018 at 9:00 AM Eastern Time.
Registration opens to all Members on Wednesday, June 20, 2018 at 9:00 AM Eastern Time.
Registration is online only. Be logged in to your DVC account and ready to go at 9AM just in case but I have never seen it sold out before it opened up to people without hotel reservations. Note that there are no "tickets", you are just on a list and you check in with ID and DVC card at the park or your resort and get a wrist band.
I have not done the Epcot event, only AK, but is was great fun. Nice to get a few "freebies" like food and drink. No free booze

Park was not crowded. Its also nice that you can get guests in the park for free if you might be in that situation. I had planned to bring my parents but they decided not to drive down with Hurricane Irma coming to town.
The others can chime in on the Epcot details but I would highly recommend it.