I did a complete tutorial for the 4x4 a while ago. It was in 3 easy parts. You do need to be able to solve a 3x3 first. The method is called reduction. Basically you match up the centres, then pair up the double edges (dedges) with each other, then you solve it like a 3x3. There are also a couple of parity cases that need fixing. My original vid deals with them well, but my newer Mega Parity vid covers them better, so I've put it here as well.Part 1Part 2Part 3Mega parity vid
Please take off topic discussion off this forum. Thanks.