To use your iPod Touch 4G without any imposed restriction of the manufacturer you need to jailbreak it. For untethered Jailbreak on iOS 5.1.1 of your iPod Touch 4G follow the directions given below.
At first download the most updated version of Absinthe from the following.
Extract absinthe-win-2.0 from the archive you have downloaded.
Make a double click on absinthe-win file to continue with Untethered jailbreak on iOS 5.1.1.
A new folder of absinthe-win-2.0 will be created with your previous action.
Now open this new folder to launch absinthe.exe.
Follow the direction and connect your iPod Touch 4G via USB to the Computer.
It is time to begin untethered Jailbreak your iPod Touch 4G. Click on the jailbreak button.
After several different steps the jailbreak on iOS 5.1.1 would become complete. It starts from beginning of jailbreak after that sending initial data of jailbreak then sending final jailbreak data. At the end waiting for reboot of device and for the completion of the iPod Touch 4G Jailbreak process.
You will be informed that the Jailbreak is done.
It would take few moments to show Cydia on your springboard.
*If the process is not done perfectly you can repeat it but always form a back up to start it.