You just need to win a ranked match, which is easy for long-time SF players, not so easy if you are new to fighting games.
If you are having trouble winning, I'd suggest spending time in practice mode learning your special moves. You might also want to try picking a character other than Ryu or Ken. Most good players know how to defeat them handily and the hadouken spam that works well at the easy arcade levels won't work against a human (ditto for Zangief's lariats). Juri has good attacks and is totally new so she might be a good choice.
There's really no getting around practicing a lot if you want to get good at Street Fighter. Try spending 20-30 min in training mode every time you fire the game up to work on your specials until you can pull them off easily.
The paper Prima guidebook for SSFIV is actually pretty good. You might want to invest in that if you are looking to improve.