How can I start learning law?

I'm not sure if you're speaking practically, or intellectually.

I would start by studying the difference between criminal and civil law. Criminal law is what you see on TV, law and order--people getting into trouble with the law for committing an actual crime. Civil law is essentially suing someone for causing damage to you. This includes suing someone for breaking a contract, suing someone for not shoveling their steps so you slip and fall on them, or any other type of lawsuit that is not criminal.

Once you begin to separate the two, the doors open to specializing a bit. First, do you want to focus on criminal law so you can tell your friends what to do or say when stopped by a police officer, or questioned by a detective? Do you want to know just how far you can go without committing a felony? What constitutes a "felony"?

Or you can start to study things like contracts, torts, and tax law. I would make a tree to see the type of things you're most interested in knowing the law behind, and then start from the basics and work into it. Maybe you're very interested in politics and want to know the law behind campaign finances? Or, like me, you have an interest in helping families so you want to know the law behind divorce and somewhat-amicable splitting of assets.

Start from basic and get more specific.