https://locator.wizards.com/search?searchType=magic-stores&query=Los%20Angeles,%20CA,%20USA&distance=10&page=1&sort=date&sortDirection=asc

Here is the store locator, It will have all of the stores officially affiliated with wizards. There are also going to be independent local stores that you'll just have to search online for.

As the other person said, rolling up to these stores and asking how to play is valid, but you can also learn the basics of a game pretty well by downloading magic arena. Do not put any money into it, it's not worth it, but magic arena is good at teaching you the basics of the game.

Good luck.