The order are constantly recruiting humans for all kinds of work they need done on Earth. You can imagine something like the men in black and that would be an accurate description of what it would be like to get contacted by the order. You would have to renounce your life and become a person who is no longer involved in any human activities. You will be sent to work in places that are not accessible to other humans. There is also another kind of recruit and it’s the people who get to work as spies and remain part of society. They continue to have regular jobs, but they get paid extra to become informants of the order.
This is a very common recruitment and the order has more than 2 million recruits worldwide in key locations. There are some requirements to be selected, but they are mostly related to investigative skills.