My front bumper is coming loose

I recently bout a used 2015 Hyundai Accent. The dealer pointed out that the front bumper was coming loose, and that it would be repaired. When I picked it up, he said that his guy had put a clip on it to fix it, and it did look repaired. Now it is loose again, and I am afraid that if it rubs up against something, it may get worse.

Before I go through the hassle of trying to get the dealer to repair the problem again, how could I fix the problem myself. It is on the passenger side, and the plastic separates for about 7 inches.

Thanks!