The image is from ours, the Instatrunk. But they are close.
You need these "wellnuts" or inserts, as Neil is suggesting. Once they're installed, they kinda stay with the Jeep, so it's not surprising they weren't included with your trunk.
I do not know if they are a NAPA/hardware store type item or not.
I know you can call and get them from us, but not positive if they will fit MOPAR trunk.