Ultrasn0w 0.9.3 is available in Cydia stores using the repo repo666.ultrasn0w.com. To add a repo go to the Cydia store and add it as a new repository.
However, before you unlock your iPhone, you will have to jailbreak iPhone . The only tool that can jailbreak iOS4 right now is the
redsn0w tool, which is available for both Windows and Mac users.
The Cydia store will only be available after you have jailbroken your iPhone.
The first iOS 4.0 unlock tool Ultrasn0w 0.93 has been released by iPhone dev team though iOS 4.0 jailbreak tool is yet to be released. This time iPhone dev team has got Ultrasn0w 0.93 Unlock tool for iOS 4.0 with Baseband 05.13.04 to 04.26.08, meaning those users who upgraded iOS 4.0 preserving baseband can also unlock iOS 4.0 with Ultrasn0w 0.93.
Now those users who don’t know how to Unlock iOS 4.0 can follow below step by step guide,
Please Note: T-Mobile USA users must disable 3G before proceeding to unlock iOS 4.0 on iPhone 3G & 3GS.
How to Unlock iOS 4.0 Baseband 05.13.04 on iPhone 3G/3GS
1. Jailbreak iOS 4.0 using Redsn0w (should be released any time soon)
2. Now start Cydia and go to Manage section
3. Now click on sources and click on edit to add following repo
Repo666.ultrasn0w.com (it’s ‘0(zero)’ and not ‘o’)
4. Now search for Ultrasn0w 0.93 and click on install
5. Let Ultrasn0w 0.93 to complete unlocking
If you rely on hacktivation or a carrier unlock (ultrasn0w) then you should not upgrade until Dev team have fully tested and released there tools.