bulb can be accessed through the back. Youll need to move around some plastics as well to get to it. Itll look like this generally; https://www.amazon.com/Poweka-Taillight-Shenke-IceBear-Scooter/dp/B00B7EVGPQ

in terms of a replacement, once you get it out you should be able to find one at any autozone.