Step 1: Download Limera1n for windows (Download Link) filesize 320kb.
Step 2: Make sure that you are having iPhone 3GS, iPod Touch 3G, iPad, iPhone 4, iPod Touch 4G running iOS 4.0 or later (up to iOS 4.1).
Step 3: Launch Limera1n by double clicking the executable file. ( similar to blackra1n )
Step 4: Connect our iDevice to your PC and click the big button thats written “make it ra1n”.
Step 5: The device must then be put into DFU manually as shown in screenshot below. To do this, hold both HOME and POWER button together.
Step 6: Once done, you would have cydia in your iDevices. If cydia does not show up, give the device a reboot. Currently limera1n is only in Windows while our friends on Mac would have to wait a while for limera1n’s updates or for greenp0is0n to be released.