Who are the protagonist and antagonist in the first twilight book? is the protagonist Edward and the antagonist James?

The protagonist or main character in Twilight is Bella. The story is primarily told from her point of view and the audience struggles along with her as she makes decisions about her relationship with Edward and the rest of the Cullens. One could argue that Edward and the rest of his "family" also play a protagonist role as many of the central events revolve around their roles.

James is definitely an antagonist. His desire to hunt down Bella and his attempt to kill her places him in direct conflict with her protagonist role.

Edited to say that protagonists are often referred to as "good guys" while antagonists are often referred to as "bad guys." While that does not always prove true, in Twilight it does.