Here’s how it works.
Select a data category group and a data category.
Then add the topics that you want to assign to the articles under that data category.
You can also select the option to add the topics to existing articles in the data category. The topics are then assigned to all articles in all data categories under the data category group. If you don’t select this option, the topics are added only to new articles added to the data category, and the existing articles remain unchanged.
After you click Save, it takes a few minutes to add the topics to existing articles. Topic assignments are community-specific. If you use the same article in two different communities, set up automatic assignments in both communities.
How does this work for translated articles? If a translation of a topic is available in Salesforce, the translated article is tagged with the corresponding translated topic. If there’s no translated topic in the system, localized articles are tagged with the base language topic.