on Fiction University:

The wrong protagonist is a serious issue for a first draft, but one that does happen from time to time. We get an idea, we write it, and it turns out that the person we thought was at the center of everything really isn’t.
This can be disheartening, but it’s not the end of the world or the end of the novel. Go ahead and vent to your writer buddies about your frustration, then roll up your sleeves and get to work fixing the problem.
To find the right protagonist for your novel: