How to add custom css file to subtheme of omega kickstart theme?
I was missing one line in code. here is what you have to do. in your .info file under optional css code write the following code. 

css[yourcustomcss.css][name] = Your custom products styles 
css[yourcustomcss.css][description] = This file holds all the product page CSS of your theme. 
css[yourcustomcss.css][options][weight] = 12 
settings[alpha_css][yourcustomcss.css] = 'yourcustomcss.css' 


Now go and enable your 'yourcustomcss.css' in Appearance/yourthemename/settings/toggle-styles