Ocelots are found in jungle biomes, and are tamed by feeding them raw fish. You'll need some patience to do this. With the raw fish in your hand, you need to crouch and slowly walk to the ocelot. Once it notices you, it will slowly walk towards you, and you can feed it once it is close enough. It is tamed when hearts pop up. If you uncrouch or move too quickly, you'll just scare it away.