how do I wipe my son's damaged (screen broken) iphone 4 using itues?

Hi noreenoverholt,

I understand you want to completely erase your son’s iPhone 4 using iTunes. The process you are looking for is called a restore. You will want to restore the iPhone and set it up as new. There are great steps that walk you through and show you how to go through the restore in the following article.

Use iTunes to restore your iOS device to factory settings

http://support.apple.com/kb/ht1414

Thanks for reaching out,

-Joe

Here are the steps to erase iPhone using iTunes:

1. Disable “Find My iPhone” in “Settings” > “iCloud” if you have turned it on;
2. Connect your iPhone to your computer and launch iTunes;
3. Select the iPhone when it is found by iTunes;
4. In the “Summary” tab, backup your iPhone with either iTunes or iCloud using the “Backup Now” button if you want to restore the iPhone again;
5. When the backup is finished. Click the “Restore iPhone…” button in the same panel and then “Restore” in the pop-up to erase all the content and settings on your iPhone.

In addition, the method 3, 4, 5 in the article 5 Methods to Erase iPhone Completely and Securely will also be helpful.