To show the Acrolinx Sidebar, select an unpublished article in Salesforce Knowledge and click Edit Article.
If you want to edit an article that's already published, click Edit as Draft to show the Sidebar.
The article opens in the Acrolinx editor, where you can check and update your content with Acrolinx. When you're done, click Save at the bottom of the page. You'll return to the article overview, with your updated content ready to publish.
Acrolinx checks all content that is displayed in the Acrolinx editor. As a Salesforce admin you can configure which fields are shown in the Acrolinx editor.