How do I replace the high mount third brake light on a 2002 gmc envoy?

Did you check your license plate lights?, because that was my problem and I was about to replace the light, but I saw that the license plate lights were off, soon as I replace them my third brake light comes on!!

How do I do it

I took mine to the dealer beacuse I bought the extended warranty. They had to replace the whole back panel because they told me that they don't make the part anymore..