Step 1: Download redsn0w 0.9.9 beta 4 using our Jailbreak Programs Tool
Step 2: Download your device firmware using our iOS Versions Tool
Step 3: Open redsn0w and then browse to the file you downloaded on step 2
Step 4: Push the next button and choose your options (Don`t forget about Install Cydia)
Step 5: Put your phone in DFU mode and press next to implement the jailbreak solution
Step 6: To boot in tethered mode and use Cydia, Safari and other apps you need to put your device in DFU mode again, open redsn0w, load the iOS, push next and select Just boot tethered now option
Your device is now jailbroken!