Probably at the beginning of the week before the event, as this gives you a chance to introduce the event before it starts. Students use the access code on the card and then choose their own username and password. You will need to remind your students not to lose these! They will need the username and password to get on the site each time.
Please do encourage them to leave an email address at registration. We won’t spam them and will only use it for this event. But it does make life a lot easier if they forget their password. It also means they get an email telling them about each eviction, which helps to make it seem exciting!