We're in the process of updating the documentation for Zotero 5.0. Some documentation may be outdated in the meantime. Thanks for your understanding.
The Style Manager displays the currently installed citation styles and the date they were last updated. You can add CSL styles by clicking the “+” button and locating the style file on your computer, or you can click the “Get additional styles…” link to visit the Zotero Style Repository. To delete a style, select the style and click the “-” button.
Include URLs of paper articles in references – When unchecked, Zotero will only include a URL when citing journal, magazine, and newspaper articles when the article does not have a page range specified.