I would actually disagree with the above if your are already familiar with the basic concepts. I do not think you will learn much more than that in these freerolls.
You would be better off starting with a $20 dollar deposit (look at it like an investment in your training) and playing micro (2NL) 9 handed cash games while studying the game, playing only one table and practice paying real close attention to opponents, their playing style, range, your own range, your own style, bet sizing etc etc. After this you can then look at moving to 6max to gain more experience in your post flop play and apply the knowledge you have already built up to a looser more aggressive format. But this is just my opinion.