To have students join your club, sign in to your club leader Cyber Discovery account. Click on the "Your students" link near the top of the page, then look for the "Manage club access code" link underneath the welcome image on this page.
This page will let you generate a club access code, which you can share with your students in any way that best suits you: via a slideshow presentation or on a board in your classroom, in an email to students, over an announcement, or any other way that works best for you.
Students who want to join or change clubs can do so by signing in to their own Cyber Discovery dashboard and looking for the join/change my club link at the very top of their timeline. From this page, they can use your club access code to join your club. Once they have joined your club and completed registration for this year's programme, you will see them on your student list.