* click on setup for the Communities page --> then click on the square of colorful dots in the upper left (app launcher) --> then search for "knowledge"
* from there you can create new articles
* to find your community go to setup--> then "Quick find" search box on the left under app launcher (the square of dots), and search for "communities", then choose all communities.
* to assign topics go to "content management" and then "article management" and then choose articles to assign to topics. Create the topics under "topic management"