From Droam Prepaid SIM Encyclopedia
You can view the APN settings on your iPad in the following location:
Settings > Cellular Data > APN Settings
To edit your APN, tap each field to enter the APN settings provided by your carrier. Tap Cellular Data at the top to save the changes to the APN and return to the Cellular Data settings.
With the iPhone Configuration Utility you can set your iPad or iPhone carrier’s APN (access point name) manually in case your 3G networking isn’t working properly, which can sometimes happen for developers running beta versions of iOS. It’s a workaround to be sure, but if you need your device on-network for testing and can’t wait for newer betas, sometimes a work around is just what you need.
Follow on after the break for step-by-step instructions.
2. Go to Configuration Profiles under Library in the sidebar and then hit New in the toolbar.
3. Under General (Mandatory) enter a name for the profile you’re creating, and a unique identifier.
4. Scroll all the way to the bottom and, under Advanced, fill in your carrier’s APN info.
5. Plug in your iPad or iPhone and then select it in the sidebar under Devices.
6. Pick your profile and hit Install.
7. Approve the installation on your iPhone or iPad.