144-hr visa-free transit in Tianjin - requirements and application process?

The last two stops on our cruise are Seoul then Tianjin. Ship arrives Tianjin 0600hrs 26-4-2018 and we fly to Singapore 0930hrs 28-4-2018. We are Australian passport holders and understand we are eligible for 144-hr free transit in Tianjin. Can you help with where we apply for this? Is there an authority at the Tianjin International Port? Would we have documentation to provide to the cruise provider? Thank you for your assistance.