To replace a wheel bearing in a Nissan Altima, start by safely lifting the vehicle and removing the wheel and brake assembly from the affected wheel. Locate the wheel bearing hub assembly and remove any retaining bolts or clips securing it to the steering knuckle. Carefully separate the hub assembly from the steering knuckle, and then remove the old wheel bearing from the hub using a press or by tapping it out with a hammer and suitable tool. Install the new wheel bearing into the hub, ensuring it is properly seated, and reassemble the hub assembly onto the steering knuckle. Reinstall the wheel and brake assembly, and lower the vehicle.