How do I go about getting a job at 15? ?

Paper round or chores for neighbours are the only realistic options until you are at least 16.

Create a cv (curriculum vitae) and hand it to pretty much every business that'll accept it. Go in just ask if there's any jobs going and if you can drop off a cv. You want to be getting it in everywhere, even just to get a single job offer.

mowing lawns, doing stuff around the neighborhood, baby sitting animals or kids. walking dogs, trying to see if the local coffee shop will sell your art if your good at any kind of art. offering to rake your neighbors yards, gardening, only jobs you can get at 15 are maybe mc donalds or exc but i think you need to be 18 before you can get a job in a store or restaurant