Looking at the documentation you can do it like this assuming you have a Movie class with the appropriate migrations for title and description.
movie = TmdbMovie.find(:title => "Iron Man", :limit => 1)
@movie.title = movie.title
@movie.description = movie.description # Not sure if the returned data contains a description
@movie.save
EDIT~ In update to below comment.
Let's say you have your MovieController and a user is a searching for the movie through a search field which would be in params[:search] and the movie returned would be stored in the database. If this is being done in the index action it would look like below.
def index
movie = TmdbMovie.find(:title => params[:search], :limit => 1)
@movie = Movie.new
@movie.title = movie.title
@movie.description - movie.description
@movie.save
end