If your iPhone 3G/3GS was previously jailbroken using blackra1n and the blackra1n app was removed or deleted from the home screen, you will need to jailbreak again to install blackra1n. With cydia installer, if you do not prefer to jailbreak with blackra1n rc3 again, now you can install the blacksn0w to unlock the baseband 05.11.07 on your iPhone 3G/3GS. But, you can follow this step-by-step guide if you wish to jailbreak and unlock your iPhone 3G/3GS from scratch.
1. Launch cydia installer and navigate to “Manage” tab. Then, select “Source”.
2. Tap “Edit” follow by “Add” buttons.
3. Type “blackra1n.com” and tap “Add Source”.
Note: Once cydia has completed updating source, return to “Souce” page.
4. Tap “blackra1n.com” and select “blacksn0w”.
5. Tap “Install” follow by “Confirm” buttons to start the installation.
6. Press “Return to Cydia” once the installation has completed.
Note: Wait for your iPhone 3G/3GS to search for the network reception and it’s unlocked successfully.
If you have any problem on unlocking your iPhone 3G/3GS, leave your message on the comment below.