how do i change the rear brake light?

Hello,

In order to replace the brake light you will have to access the tail light assembly.
Open the trunk.
Remove carpeting covering the back of the taillamp assembly.
The taillamp assembly is mounted using few wingnuts. Take off those nuts.
The assembly will slide outwards.
You will have access to the lights.
Simply twist and remove the bulb and replace.

https://www.2carpros.com/articles/brake-lights-not-working
https://youtu.be/KNqxFEoNcrc

I have attached diagrams for your reference.

Please let me know of any questions.

Thank you.