If you had to explain to someone how to drive in the freeway through text, how would you?

First of all I drive on the freeway, not in it. But, all joking aside, California freeways are pretty wild during the day by my experience. If you can drive well otherwise with lots of traffic, you're already halfway there, but yes it is more difficult due to the higher speeds. I learned up here where I live before driving the wild Cali freeways, so i was more slowly introduced than you would be just suddenly merging into high speed traffic. You have to check mirrors, signal and turn your head about just as often, every time you change lanes and such. Sometimes people are courteous and let you merge into traffic, but you always have to be carefully watching everything going on around you regardless. If you're a good driver otherwise, you should be fine. Good luck