Remove the gray hook on the left side of the trunk and ground away. You might wanna sand the sheetmetal down a little to improve the ground. It's already threaded for a screw so you can just pop the screw out of the hook and use that one.

 

What are you grounding?

 

any thing thats metal! or remove the plastic piece (the lift over spot) and there is a bolt under there you can remove and attach wires there for a ground