If you want to nominate works/people for the 2021 Hugo Awards, Lodestar Award for Best Young Adult Book, and Astounding Award for Best New Writer, you must be a member of either the 2020 Worldcon (CoNZealand) or the 2021 Worldcon (DisCon III) by the end of 2020. (You can of course be a member of both, but you can only nominate once.) If you were a member of CoNZealand (Worldcon 78/Wellington, New Zealand) (supporting or attending, or any other membership class that included voting rights), you are already eligible to nominate. If you were not a member of CoNZealand and are not a member of DisCon III (Worldcon 79/Washington, DC, USA), you must join DisCon III by the end of 2020 as at least a supporting member to be eligible to nominate.
The Hugo Awards are selected by a vote of the members of the World Science Fiction Convention (Worldcon) in a two-stage process. The first stage is nominating (which starts in early 2021) and the second stage is the final ballot that includes those works/people that received enough nominations in the first stage (which starts later in 2021). If you want to participate in the nominating stage and are not yet a member of either the 2020 or 2021 Worldcons, take note of the December 31, 2020 deadline for joining Worldcon in order to be eligible to nominate in 2021.
To join the 2021 Worldcon, go to the DisCon III 2021 Membership Page. You do not have to attend DisCon III to be a member. A supporting membership includes all of the membership rights including nominating for the Hugo Awards, but not the right to attend the convention itself. Other membership classes including Attending and Young Adult also have the nominating and voting rights plus the right to attend the convention. If you join DisCon III as at least a supporting member by the end of 2020, you will be eligible to nominate for the 2021 Hugo Awards.
The final ballot will be announced sometime after nominations close. Only members of the 2021 Worldcon will be eligible to vote on the final ballot. The deadline for joining in order to vote on the final ballot is when final ballot voting closes. DisCon III 2021 has not yet announced specific dates for voting on the final ballot. The December 31, 2020 deadline applies only to joining in order to nominate, not to vote on the final ballot.
In general, the 2021 Hugo Awards and Lodestar Award are for works first published in the previous year. The Astounding Award (presented by Dell Magazines, publishers of Analog) is for authors whose first SFWA-eligible publication occurred within the past two years. Therefore the 2021 Hugo and Lodestar Awards are for works first published in 2020, and the 2021 Astounding Award is for authors first published in 2019 or 2020. There are exceptions in the Hugo and Lodestar Awards for works previously published in languages other than English, and for works originally published outside of the USA. See the section about “Year of Eligibility” on the Hugo Award Categories page for a longer discussion of this.
The 2021 Hugo Awards will be administered by the 2021 Worldcon. See the Hugo Awards web page on the 2021 Worldcon’s web site for additional information. Address specific questions about the 2021 Hugo Awards to the 2021 Worldcon. The Hugo Awards web site does not run the Hugo Awards. Each year’s Awards are run by that year’s Worldcon.