how will we develop the "character" in a story writing?

The basic answer to this (rather large question) lies in giving your character dimensions. You set up what kind of character they are, and we expect certain behaviors. Through the story you decide to tell, we want to see the complications or contradictions in the character. Look at Chekhov's "Lady with the Pet Dog." The main character is set up very clearly - a womanizer who is uninterested in anything other than his own pleasure. Through the story, we see him exhibit desperation to see the woman and then discover he is deeply affected by getting older. He is more than we thought at the beginning. So set up what the audience should expect, and then provide other layers.