First make sure you have removed any duplicates from your library before you begin to cite references in your Word document. This is important to avoid any errors in your bibliography.
Place your cursor where you want your citation to appear in your Word document and click on Add/Edit Citation.
The first time, you might see a Document Preferences dialogue box. This will give you the option to select the citation style you want.
After you have made your selection, the Citation dialog box will appear.
If you are working on a project or on a shared document with a group of colleagues, you can create a Zotero Group Library which you can use share references.
When you insert citations into your Word document, you can choose to search references in a particular group by selecting that group from the Add/Edit Citations dialogue box and then then by selecting references from those in the group.