I wanted to replace an old flood light on the outside of my home with a new motion detection one.

I went and bought one from a box store.

I removed the old flood light from the wall, and therein lied the discrepancy:

-The old one was mounted using two screws into a circular plate (kind of like this http://i.imgur.com/GWf5GFG.jpg)

-The new one only has 1 screw - in the middle.

How do I get this new one to fit in the old plate?

Thanks!