Instructions
Press the Xbox button on your controller, select "Xbox Home" and then select "Browse Apps" from the "Apps" page.
Select "Netflix" from the video section of the Xbox Marketplace, select "Download" and then select "Confirm Download" to install the Netflix app. Installation takes just a few seconds.
Select "No" when asked "Are you a Netflix member?" if you do not have a Netflix account and then select "Yes" when asked "Ready to start your free trial?" to open the Xbox 360 Web browser with the Netflix signup page. If you do have a Netflix account, select "Yes" instead and then enter your Netflix account credentials.
Enter your personal information and credit card information to start your free Netflix trial. Netflix is free for the first month and will only charge your credit card after the one-month trial is over.
Press the Xbox button to return to home, launch the Netflix app and then sign in using the account credentials you configured during the signup process.