I'm off work for today and tomorrow, and have arrived at Norwescon in SeaTac, Washington. This is one of the three places where Worldcon 76 will be doing a live announcement of the 2018 and 1943 Hugo Award Finalists. The other two events are an open-to-the-publin event at the 7 Stars Bar & Grill in San Jose, and an event at FollyCon/Eastercon 2018 in the UK. The announcements will be at Noon Pacific Daylight Time (8 PM British Summer Time) on Saturday, March 31, 2018. (Not April 1, although as others have pointed out, it will be April 1 at SF/F conventions in Australia and New Zealand.) I'm sorry we did not manage to find people to do similar live events at other SF/F conventions this weekend, and I'm partially to blame for not having beat the bushes better.
Shortly after the live events (probably round 1 PM PDT, but I wouldn't guarantee that to the second), the video and the finalist lists will also be posted on the Worldcon 76 web site and on TheHugoAwards.org.
Voting will open sometime in April. We're not going to commit to a specific date yet. You have to be a member of Worldcon 76 (and only Worldcon 76) as of when you vote. The deadline for joining is the same as the deadline for voting (unlike the nominating ballot), but if you are planning on voting on the final ballot, I encourage you to join as at least a supporting member now and not put if off to the last minute, where a computer failure could leave you in the lurch.