QuickPwn 3.x has not been released.
Steps: Download version 2.2.5 of QuickPwn Mac. This will come in the form of an Apple disk image file.
Do not run off the disk image, first copy QuickPwn to your hard disk.
Do not download a .zip file instead.
Use iTunes to upgrade to the latest firmware. QuickPwn runs on already upgraded un-jailbroken iPhones.
This method does upgrade your baseband, which means it will negatively affect unlocked phones. You should read below for details.
I (saurik) have not had a chance to use this tool yet. However, I have received many glowing reports of it.