Once you get your phone, go to Settings>Mail,Contacts,Calendars and add your gmail account. From this screen, you will also find "Fetch New Data" and by clicking on that you can choose to turn on Push, or, select Fetch and its timing intervals. Unfortunately, gmail is only fetch or manual on the iphone without tweating.....but not push. Therefore I have "Every 15 Minutes" selected.
Originally Posted by glisk74
Edit: Sorry, your question was answered while I was typing this. Just follow the instructions for setting up Push as previously mentioned.