To get immediate results from Noise Ninja, try the following:
1. Click on the Profile Image button on the Profile page. This will
measure the noise in the image.
2. Adjust the Luminance Strength slider on the Filter page until you
like the results.
3. Go to the Noise Brush page. Paint with the brush tool in the Preview
window to protect parts of the image from filtering.
4. Press the OK button to filter the entire image.
This procedure should yield reasonable results for many images. However, your workflow will probably be more productive and consistent if you learn to use more advanced features like camera profiles, automatic profile loading, and actions.