I would assume that it would work like most other online secret santas, such as reddit, where people enter into it with a username and address within a certain frame of time. Once the time ends, the users are randomly paired up with 1 other user. After you get the name of the user, it's up to you to either ask them questions in regards to what they like, or to just surprise them with a gift. Some people put a lot of time and care into being someone else's "santa", while others.. well.. kind of dont haha, so YMMV. It's a really cool concept, though, especially in a more specified hobbyist setting, where you know you're going to get something cool/useful.