Ok, so you know what RPing is, and you're just eager to know how to do it, aren't you?
First off, the very beginning, you need a character to play. You can chose a character from Naruto TV show or make a fan character. Note that the fan character can be a character from another TV show, but it must be a manga.
Right, so you have your character, and your setting, now what do you do? Well, start at the beginning obviously, introduce your character. When you first make an entrance, make sure you know where everybody else is (so you don't put "walks into the room" and everybody is in a forest miles away), then enter, briefly describe your character, maybe a little history or personality mixed in with, but not too much, they don't need your life story yet.
And now you rp! Don't worry, I'm not going to leave it at that.
Basically what you need to do is act, only type it. What would your character do in the situation being played out in text on screen? Type it, actions and words. Make sure to keep to character, if your person is supposed to be soft hearted, kind and gentle, don't make her yell at people and kill them (unless, of course, that's just another face of their personality.)
Gaara of the Desert
Choji Akimichi
Sakura Haruno
Tony Tony Chopper