I have a totally different opinion here.
If you are going to play poker, I mean actually play the game, you need to play for money. Money adds the sense of loss to the game. If you are just playing for chips that is all well and good to figure out which hands beat which other hands. But when there isn't money involved, there is nothing to stop you from betting like a maniac and losing. When you are set to lose say a hundred bucks, you will tend to think a bit before you act.
This is where the real fun begins. Learning odds of hitting your draw, learning how to understand your opponents and how to manipulate them with your play while not letting yourself be manipulated.
Basically poker play without money involved is a waste of time. I understand that you are new to the game and afraid of 'losing the house'. It is near impossible to develop a real sense of the game if there is nothing being wagered.
I personally think that the money you use to play with should be enough to hurt should you lose it, but not enough to leave your in financial ruin. This way it will sharpen your thought process.
You will find that your opponents are different when you play for real money too.
In the free online games when you bust out, just hit the button and you are back in. Nothing wagered, nothing gained.
This of course is just my opinion.
Now in answer to the question of how to learn, there are many online poker resources that will teach good thought principles and I fully recommend some reading. To actually learn these principles you will have to play the game.
So read instructional material and play the game. That is the best way (IMHO) of learning it.
Have a google search for Noted Poker Authority. Its a good site with TONS of information, all texas hold'em specific.