If you have A-4 device including iPhone 4 CDMA, iPhone 4 GSM, iPod Touch 4G or iPhone 3GS then guide below will help you for tethered iOS 6.1 beta 5 jailbreak by using RedSn0w for Windows and Mac.
Note: You can perform untethered iPhone 3GS (old-bootrom) jailbreak by following guide below. Only developers can perform iOS 6.1 beta 5 tethered jailbreak with RedSn0w.
Jailbreak iOS 6.1 Beta 5 Tethered using RedSn0w
On Windows right click on extracted RedSn0w.exe file, on Mac press “Ctrl” and click on extracted RedSn0w app file and then click on “Open”
Click “Extras” button on RedSn0w screen
Click “Select IPSW” button and select the downloaded iOS 6 firmware file (not iOS 6.1 beta 5). Once RedSn0w recognizes the given firmware file click on “Back” button
Click on “Jailbreak” button, and follow the on screen instructions carefully to enter into DFU mode
Once your iDevice entered into DFU mode, RedSn0w will start processing with iOS 6.1 b5
Select “Install Cydia” option and click Next button to initiate jailbreak process
When RedSn0w will complete the process, your iDevice will reboot into a non-jailbroken state, this is because of tethered jailbreak so you need to boot through RedSn0w
Now, again put your iDevice into DFU mode through RedSn0w
From main screen of RedSn0w, click “Extras” > “Just Boot” for a tethered boot of your iDevice and thats it