You start by filling out an application on their website. Be sure to have a Resume, List of References, Cover Letter and Salary History also ready at the time of submission. Many times all four documents are required, some times only a Resume and Cover Letter are required in addition to the standard application.
Most likely there will be two rounds of interviews if your application is accepted. They are the standard interview questions about yourself and experience. There will often be a couple or few situation questions.