Submit to the iOS App Store
To submit to the iOS app store, you must have a valid developer account.
First, make sure you've tested your app on a device, and everything looks good. If you are using push notifications, use an ad hoc certificate and make sure they are working correctly.
Next, build your app in PhoneGap Build using an app store certificate and profile.
Download the .ipa file, you will submit this to iTunes Connect.
Login to iTunes Connect, click My Apps, then + to add a new one. Fill out the required fields, then submit your app for review.
You can find a more detailed tutorial here.