This jailbreak supports the following iDevices and firmwares but How to use it to JailbreakMe 3.0 for your iDevices – Iphone 4, 3gs, 3g – Ipad 1,2 – Ipod.
Step 1: Just Open This link from Your iDevice

Http://IphoneHowtojailbreak.com/jailbreakme/

Step 2: Goto your device and choose which firmware you want to Jailbreak with JailbreakMe
If You want to see The video Go to This Post