Be VERY careful as the rods have a lot of stored energy in them.
I'd recommend laying some very heavy blankets across your back window and surrounding areas before attempting the removal/installation.
You can put a pipe over the exposed end of the rod to use a lever to lift it out of the slot.
Be aware also that there are 2 different sized rods and different rods used for cars with rear spoilers vs non-spoiler cars.
Again be careful with these as they can snap, twist, break.... damaging YOU or the car.
Wear safety glasses and heavy gloves.