There are two ways to get your password sorted out, depending on what stage of the account creation process you are at, so if initially the instructions don't appear to apply to your case, just keep reading.
When you created your account
When you created your account you would have been presented with a screen like this:
You would have been sent an email (check your spam folders too) with a link to validate your account and set your password. The email had info like this:
When you click on the blue link "Validate account and set password" you are taken to this page:
Click on the blue Log in button and you are taken to a form where you can set your password and also change any details you may have entered incorrectly:
Enter your new password twice, scroll to the very bottom and click 
You are left on the same page, but you will see this message at the top: 
If you are unable to find the email that was sent when you created your account (OR you simply forgot your password).
First, go to:
https://ballot.fwf.net.nz/user/password
which looks like this:
(you can also get to this page by clicking on 'Log in' at the top right, and then selecting the 'Reset your password' tab).
Enter the email address or user-name that you used when you created your account and you will be sent an email with a link.
NOTE: If you enter the user-name or password incorrectly, you will get an error like this:
)
You may need to cut and paste the link from the email into your browser, but it will take you to a page that looks like:
Click the blue "Log in" button, and that will take you to the screen described above where you can set your password.