slide the end facing the the middle of the car in first, at an angle. Wait for it to catch the hook, then slide it fully into place. When the outside end is alsomost flush, give it a firm push and it should clip into place.
If it doesn't, you probably broke the mounting tab when you removed it.
<span style='color:gray'><span style='font-family:Courier'>1995 e36 3 Series RIP
1999 e46 3 Series BURN IN HELL
2000 MR-S Roadster= Current</span></span>