trying to minor in ML

i got into accepted into UCSD for class of 2030 as a cogsci major and i want to minor in either machine learning or compsci (most likely machine learning cus i want to work in the ai/ML field) but im not sure how i would apply for a minor. would i need to do it as soon as i get to school? or do i do it in a specific year? i have no idea where to start i know nothing about minors.