You should only have to navigate to netflix.com, log on to your account and play a movie.
The only thing you need to install is Silverlight, and Netflix should prompt you to do that when you try to play a movie (if Silverlight is not already installed on your Mac).
Here are the instructions from the Netflix Help Center:
For system requirements, see our Complete System Requirements for Silverlight article.
Follow the steps below to install Microsoft Silverlight:
- Click on any title to play.
- Click Install Now.
- Click Save File.
- Double-click Silverlight.dmg in Downloads.
- For Safari, the Downloads menu is in the upper right-hand corner of the browser.
- For Firefox, Downloads is a separate window located in the Dock.
- Right-click or hold Control on your keyboard and click on Silverlight.pkg.
- Click Open on the pop-up menu.
- Click Open on the prompt that says "Silverlight.pkg" is not from the Mac App Store. Are you sure you want to open it? Opening "Silverlight.pkg" will always allow it to run on this Mac.
- Follow the prompts to complete installation.