To make it simple. right from the contacts app in mac osx, in the preferences there is an option to export and you can select Gmail as one of the default options listed. it is really easy but i'm not next to my mac so i can't give exact instructions.
it could be the same thing as BacknBlack said but i was just giving a little extra detail
Any email program should export contacts as .csv files. If you do this and then import them into the gmail account that is tied to your phone, you will have all the contacts pushed to your phone.