HELP PLEASE

My refridgerator needs a new Gasket which i have just installed. At first my door wouldn't stay shut at all. It didn't go on very good but after being on for a day it is finally starting to want to close and stay shut. Any suggestions on why the door won't stay shut, it's like the gasket is not working correctly It doesn't hold the door shut.

I've tried everything, tilting the fridge, moving around the gasket (this helped some) but is there a trick to getting this piece on there correctly?

Part:
AP2115016 (218730614) - Gasket -