Once the two central under trays are installed move to install the two Rear/Fuel Tank under trays. Here you can see them side by side.

There is a stock, fuel tank under tray protector that is quite small and not nearly as protective as the ones you're looking to install. Remove it by taking out the bolts and clips and put it aside.

Here you can see that a flat head screw driver will also work just as well to remove the plastic clips in the underside.