@ruth0709 There are 3 steps in the 457 visa. Sponsorship, nomination and visa application. the first two are the company's responsibility. The company should be allowed to sponsor workers (if not, they need to apply first), then nomination (they will nominate you for the position and again wait for the approval from DIBP). After the nomination, you can apply for the working visa (457).
This is based on my experience last 2013. I am not sure if things changed.