In order to use the VoterVoice API, you need to be an advanced-level client. If you have a standard-level system, please contact your account manager to discuss upgrading.
You will also need an API Key. Contact firstname.lastname@example.org, and the Support Team will send you that key via a link that can only be accessed once.
You can find the wiki for the VoterVoice API here. That includes the documentation for all the current calls.