how does the Great Gatsby follow the steps of narrative structure(exposition, rising action, climax, falling action, resolution/denouement)

Just think of Gatsby as your central character and place events involving him in order of the narrative structure.

Early in the novel we learn that people know who Gatsby is, that he has a ton of money, and that he lives close to our other characters.  We also learn a little about Tom and Daisy's marriage.  This is introduction, or exposition.

Then, we learn that Daisy and Gatsby had a relationship earlier and that Gatsby's intentions in coming back were to win back Daisy.  He goes through great pains to arrange this.  These are acts of rising action.

The climax, or conflict, occurs when our central character faces a change in power.  Up until this point, Gatsby was slowly gaining power in the wooing of Daisy.  The conflict occurs in the hotel room when Gatsby and Tom force Daisy to make a decision and she doesn't make a clear-cut one.

Falling action happens very rapidly in the novel with Daisy and Tom going home and staying there.  Most of the falling action occurs outside the narration as Tom has a secret conversation with Wilson leading Wilson to head over to Gatsby's house.

The obvious resolution of this novel is the killing of our central character and the attempt of Tom and Daisy to stay together.