rounding off corners...?

 From:  theghost
8738.1 
Hi all, I've been watching a tut on Youtube called "Moi3D hard surface" and have been following along but have run into a wall. What am I doing wrong? I'm trying round off the corners. He used the fillet tool which doesn't work for me yet I would have the the chamfer tool would be better to use. In any case that didn't work either. If I'm missing something please let me know.

Cheers