I would start off with reading books while playing "play money" games at one of the many sites that offer it. A few books that i would read are David Sklansky's "theory of poker", Brunson's "super system", Caro's book of Poker tells (more to learn how to avoid showing your own tells).
After you have played enough "Play money" where you are consistently winning, i would start off at the lowest stakes limit poker games and then moving your way up to higher and higher limits as you discover that you are consistently beating the lower limits. it can take months before you are playing decent level limits.
I have been playing poker since i was 6 or 7 so the basics of the game was something i never had to "learn." So i am not sure if you need to get a true beginners book, but the books i recommended should cover what you need. If not you can probably get any beginners book to learn the basics.
I have plenty of friends that have tried online poker and they are all down in the long term. So make sure you learn the game very well before playing and also learn the patience that is needed to deal with the ups and downs poker hands you.
If you have any questions, you can shoot me an email at
gambling1015@aol.com and i can do my best to guide through some information that i wasn't aware of before i started playing. good luck either way.