Elections are held in the middle of Spring Quarter of the school year. When that time comes, you can apply for the positions you want to run for (you can even run for multiple!). For each application, you must write about why you believe you are the right candidate for that position.
On election day, make sure to dress nice! All board members, staff, and candidates will be present to listen to candidates give their speech. Other candidates running for the same position will leave the room. After all candidates have given their speeches, everyone will vote. If you are elected to a position, congratulations!
The CASA Constitution has everything you need about positions, their responsibilities, and the election process. It can be downloaded here