Zotero is the best choice for Mac users. It also plays nicely with PC's.
At https://www.Zotero.org/download/, click to download BOTH Zotero AND the Zotero Connector. You need both tools, working together:
To export a citation from OneSearch, a library database, Google Scholar or another website to Zotero, make sure your Zotero desktop application is OPEN. Click on the title of the article (from your search results). Then click the button in the far right corner of your browser (circled here).
Within Word, to add a citation or Bibliography, click the Zotero button, and you can choose how to proceed:
