1. Book ticket from https://www.buquebus.com – book in advance for cheaper tickets; the ticket I bought the night before had its price doubled. The return ticket I bought on the day itself was tripled in price.
2. Get to Darsena Norte – https://www.buquebus.com/BQBWebV2/web/Estatica?html=FAQ.html
It was easy, I dropped nearby and asked around and walked to the ferry terminal. Everyone knows where it is.
3. Buy ticket, or redeem online purchase for actual ticket (still need to queue to do so – note to go slightly earlier)
I was surprised at how developed and comfortable the ferry was. It was selling food, had a shop within it, had multiple stories (seen in last picture), and was extremely comfortable.