Antenna removal, how to?

[rick_od]

Today i got the rear water leak. I removed the 3rd brake light to look around. My headliner on the drivers rear is where its wet but water can come in from anywhere. With the 3rd brake light out you are actually looking at the back side of the headliner so if it were leaking there i think i would see it. While there i noticed the antenna was a bit loose. That didnt look like it was leaking either but i wanted to see if i could tighten it up a bit just in case.
Anyone have an idea as to how its attached or how i would be able to tighten it up?
Thanks!