Zotero has an official plugin for Microsoft Word (as well as LibreOffice), which are included in the installation package. After installing Zotero, the program will detect whether you have Word or LibreOffice installed and offer to install the plugin. Doing so has several benefits. The plugin will add a ribbon to the top of Word allowing you to add citations and bibliographies from your library, and additionally it will track your usage of each citation and automatically replace subsequent citations to a source with id. or supra as appropriate.
There are two primary methods of adding citations to a document from Zotero: