The rear light will have one wire that goes into the bottom of the light that you can just unplug by pulling. The other one that goes to a ring terminal on the lamp mounting bolt. Depending on how it's been done you can either unplug from the ring terminal and undo the bolt and take the ring off.
I'd recommend the latter as there's no guarantee they'll send you a new one with a replacement light.
The rear light will have one wire that goes into the bottom of the light that you can just unplug by pulling. The other one that goes to a ring terminal on the lamp mounting bolt. Depending on how it's been done you can either unplug from the ring terminal and undo the bolt and take the ring off.
I'd recommend the latter as there's no guarantee they'll send you a new one with a replacement light.