From what I have heard the Portuguese Hostel Association has pretty much stopped functioning, but they used to have a list of all the requirements. I would recommend getting in touch with someone who was involved in the organization to ask them for details. I don’t know who would receive an email now, but you could try sending a message to [email protected]. If no one gets back to you, perhaps you could reach out to Ricardo from Poets Hostels, Joao from Destination Hostels, or Rui from Rivoli Cinema Hostel. They were all former presidents of the Association, so they might have the info you need.