If you want some help with the learning process, you can seek out a trainer. Or you could take a look at the guide I wrote. Just the first few pages have some basic concepts that can be really helpful if you don't already know them.
Watching replays is very important for improving, but you need to know what to look for. The main thing is to try to figure out which side is winning vs. losing. When you get a sense of what is a winning position vs. a losing position, then you can try to figure out HOW each of those players is putting themselves into a winning vs. losing position.