Mapping news to stores is how you determine which news articles are visible on which stores. These items will not appear in the sitemap or on the news page, and are not accessible even by direct URL on stores they're not mapped to.
1 - First, if you want content to vary from store to store, you need to set the AllowNewsFiltering GlobalConfig to true.
2 - Next, go to Configuration -> Store Maintenance and click on the 'Contents' tab, then choose the store you wish to change mappings for from the dropdown menu at the upper left of the page:
3 - After the page refreshes, the chosen store's content mappings will be shown:
4 - Check off the box(es) for the news article(s) that you want to appear on this store, then click the 'Save' link at the top of the section being changed.
NOTE: You can only check off boxes on one page at a time. Please click 'Save' before moving to the next page of mappings to change!