Basically, there are only a few steps, but one of them is extremely important: typing the correct filename of the sitemap.

1. Log in to Webmaster Tools and click on the site profile you want to submit a news sitemap for

2. From the left navigation menu select "Site configuration" then click "Sitemaps"

3. Click on the "Submit a Sitemap" button (figure 1)

Figure 1

4. In the field which appears, type the filename of your news sitemap then hit submit. (figure 1)

Figure 2

You're Done! If the sitemap is formatted correctly and Google can download it from your server, You will see a green tick next to the news sitemap. Note that processing the sitemaps may take a while, please be patient.

If you see a red "x" next to the sitemap, click on the sitemap filename to see detailed information about what is Google's issue with it.