Zotero offers word processing plugins for Word and OpenOffice. The plugin adds a Zotero toolbar to your word processor that allows you to add citations to your document while you write.
To add a citation, click the first button ("Insert Citation") on the toolbar. Select the reference you want to cite and click OK. Zotero will add the citation at your cursor.
At the end of your paper, click the third button ("Insert Bibliography"). Your bibliography will appear, and new citations will be added automatically. Change bibliographic styles with the last button on the toolbar ("Set Document Prefs").
Full Instructions: https://www.zotero.org/support/word_processor_integration
To create a bibliography or a citations list in Zotero, highlight one or more references and then right-click (or control-click on Macs) to select “Create Bibliography from Selected Item(s)…”. Then select a citation style for your citation/bibliography format and choose either to create a list of Citations/Notes or a Bibliography. Then choose one of the following four ways to create your citation/bibliography:
Save as RTF will allow you to save the bibliography as a rich text file.
Save as HTML will allow you to save the bibliography as a HTML file for viewing in a web browser. This format will also embed metadata allowing other Zotero users viewing the document to capture bibliographic information.
Copy to Clipboard will allow you to save the bibliography to your clipboard to paste into any text field.
Print will send your bibliography straight to a printer.
Full Instructions: https://www.zotero.org/support/creating_bibliographies