Option 1: if you want to register a new team, and you and your team mates satisfy the required conditions to be eligible for the prizes (check the Rules for this) then pick Option 1: register a new team. You will also have to provide details about your school and contact details for a teacher nominated by you. After you have successfully completed the registration, your team mates can register to join the team by picking Option 2 below.
Option 2: if one of your team mates already registered the team and you want to join that team then choose Option 2: join an existing team. If you choose this option then the person who registered the team you want to join will have to confirm (s)he is happy for you to join by clicking a link sent to his or her email.
Option 3: finally, if you are not eligible for the prizes, for instance because you or any of your team mates are not a student in the UK or are too old, then you can still register a team by choosing Option 3: register a new non-competing team. This option is for instance suitable if you are a teacher and would like to follow the competition closely. It allows you to do a lot of the things the `regular' teams can do as well, such as submitting your answers and checking whether they are correct, you can use the team notepad, etc. However you are not eligible for any prizes, your team will not show up on the leaderboard and you can not post on the forum.
Please have a read through the Rules and the FAQ before you start the registration process. (You will be asked to confirm you did during the registration). And please be aware that you are only eligible for the prizes if both you and all your team mates satisfy the conditions as set out in the Rules!