Where and how do I choose an health insurance plan

Hi, I more or less recently turned 21 and have no health insurance since im off my mother's plan. Truth be told to give context I was planning to off myself after graduation not looking for sympathy its just context for why i dont know anything or bothered to research before so im not exactly a sharp person very dull in fact but Im trying now for the fact that ive made peace and want to try to adult and advance in life that being said I dont know jack about health insurance here in Cali, when I Google it I just get the somewhat basic gist of health insurance but I dont know exactly where to go or what to do im lost in the dark here you know, does anyone have links or resources thats kind of a step by step guide to navigating this? Its confusing and like I said im not very bright but im willing to give it a shot for the sake being on top of my health for my family and me I would really appreciate it thank you.