Click on 'View installation instructions' link here - this shows you how the ends are mounted - apparently, they don't just clip in. You may be able to do this from underneath without removing the front bumper - after removing the undertray...
Nissan Front Chin Aero Deflector (unpainted) - 2009-2010 370Z :: Nissan Parts, NISMO and Nissan Accessories - Courtesyparts.com