Usually, voters in NemoVote are created by the administrator. This means, that each voter will get logins either from the administrator directly, or via the integrated bulk email function in NemoVote (send credentials function).
When the voter then logs in, they will be prompted to change that initial password and they can set their new password directly on their NemoVote home page.
This prompt will stay in place until the voter changes their initial password. They can opt to not change the password and continue with the initial password.