If you're talking about the device he uses and how it works......
There will be four rows separated by vertical lines, sorta like a slot machine. As the numbers are constantly changing, look for a number that sticks. Click on that number, do this for each row when you have a number for each row it will stock and you have hacked what ever device you were trying to hack.
In the beginning it shouldn't be too hard, but the harder the device you are hacking, the less time you have. So pay attention to all rows, cuz you never really now which row a number will stick first, so don't just hope that they will find them in order.
Also, as you advance in the game, your hacking tool will be upgraded making it a bit easier. Easier hacks will practically work without you even clicking on any rows at all.