Okay, Heres the fact, The 4x4 is called the Rubik's "revenge" because Erno Rubik wanted to get his "revenge" on everyone who had mastered the 3x3 . The Rubik's revenge is more challenging than the 3 x3 (I know, its suprising) because the 4 x4 doesn't have a designated center piece that is stationary. Since there are 16 pieces per face 16 is an even number, each piece of your Rubik's 4x4 will move independently, and therefore there is no designated center piece. The Rubik's (and EastSheen) 4 x4 can be solved by following the following steps in a nutshell.
Find the centers, match up all centers.
Match up edge pairs
Solve as a 3 x3
Now doesn't that sound easy? Once you get the hang of it, it will be pretty simple for you.