Apple controls which applications are available to iPhone users through the AppStore approval process. Many effective and useful apps are denied approval for proprietary reasons or reasons that Apple believes could potentially harm users. “Jailbreaking” the iPhone will allow the user to download apps outside of the AppStore and connect to GSM networks other than AT&T. For a few years, “jailbreaking” was a confusing and involved process that was only navigable by the most savvy users. Now, it is extremely easy to “jailbreak” the iPhone using only the native Safari browser.
Turn on the iPhone 4 by pressing the button on the top right of the device. Navigate to the home screen.
Select the Settings app. Scroll down to "General" and select it. Select "About." If the number listed next to "Version" is higher than 6.0.1, do not update, as the jailbreak only supports that firmware or lower.
Exit the Settings app. Connect the iPhone to iTunes and back up the device. This is an essential step before the jailbreak.
Open the Safari app in the iPhone. Navigate to jailbreakme.com. The window will display a page with a slider similar to the one that unlocks the iPhone when it sleeps.
Slide the button from left to right by dragging it with a finger. Safari will download the jailbreak firmware and it will install automatically.