As reported earlier this week, AT&T began to deliver multimedia messaging service (MMS) for iPhones in the U.S. on Friday.
In enabling the service, which iPhones in other countries have supported since June, AT&T is fulfilling a promise it made to enable MMS by late summer.
In order to update the iPhone to handle MMS, the device must be plugged into iTunes. If a dialog box doesn't appear immediately, click check for update.
A dialog box will then appear with the message: An update to the carrier settings for your iPhone is available. Would you like to download it now? Clicking download and update will bring the software updates to the smartphone. Download and install it, click OK when you’re done, then reboot your iPhone.