In the census configuration it is specified whether new voters can be added to the census during the voting period (open census) or not (closed census). You can also add extra fields to the census table.
In an election with closed census, the administrator, previously to the election beginning, will load a list of voters in one of two possible ways (see 'Census Data' section). With this configuration, users are not allowed to self-register themselves (there is no form by which a person can add himself to the census), but the administrator can remove and add people in section 'Census Data'.
This option allows users to register themselves in the census by filling a form during the period the election is active. The census could start from zero when the election is started or the administrator can load an initial census before starting the election and allow new votters to register themselves to the census while the election is live. The election administrator will define what data to gather from the voters participating in the election.
You can add as many extra fields to the census as you need. There will always be at least one extra field, which will be 'email' or 'tlf', depending on the authentication method chosen in the previous section.
Once the election has started a signup webpage will be created. The administrator can share it (via email, social networks, publishing in a webpage etc) inviting people to sign up and vote.