There is a vast amount of knowledge out there on computers! In fact, it is so vast that no single person could ever possibly ever learn everything there is to learn about hacking or computers in general. People usually specialize in a certain field: cryptography, computer security, networking, software development, testing, and so on...It's probably a bit premature to decide what you want your speciality to be, but keeping the question in the back of your mind will help give you direction in the future.
Well, you have made the first step by finding a blog such as this and showing an interest to learn about computers! A blog is great because you are continually receiving little bits of information. It's not the quickest way, but a great to keep up on new hacking tactics and refresh your memory on general computing techniques. If you want to progress more quickly, then the first logical step would probably be to learn how to program. Programming skills are probably the most valuable skills to have! The best way to do this is by trying out your own little projects. This could really be anything! You could create your own website, try designing a simple game or create an application for your phone, etc...Basically anything that sounds vaguely fun to you? Don't really know how to program? There are a ton of online resources at your disposal! If you don't know how to do something, simply "Google" it and chances are someone has already had a similar question. Just follow my post keep calm. You will learn about everything from SQL Injection to XSS attacks, Besides the internet, don't forget the library! Your library probably has dozens of books on programming, networking and computer security. Go pick some up and peruse them just to see what interests you? Besides it i wrote a book "Intro to hacking" you can download it for free and after reading it you can know basics of hacking. (wait link is coming soon)