Ensure the user is a Knowledge user by selecting the Checkbox of Knowledge User field in the user profile.
To create and publish Knowledge articles you will need Create and Publish permissions based on either the proper Profile or Permission Set available based on your organization.
Access All Communities
From Setup, enter Communities in the Quick Find box. Click All Communities then click the Workspaces link associated to your Community URL.
Click the Content Management tile.
These steps will show how to add topics to an article. You may sort articles with or without topics, Data Category Group and Data Category. Quickly find an article by entering the article title in the Search articles box.
Click the Topics tab (top right) then click Article Management (bottom left). Click