For Creativity, Action and Service, you have to do extra curricular activities which fall into each category.

For example
Creativity: Photography/Fine Arts classes
Action: Soccer training/games
Service: Volunteering at the local old peoples home

You have to do CAS activities for at least 2 hours a week, and include a variety of activities, that fall under, 1, 2 or 3 of the categories.
You will have a CAS Supervisor at your school who will help you with fulfilling the requirements you need for CAS.