You should be able to find most of what you need at Zotero's website, in the documentation section. The information in this section is intended to supplement what is on the official website.

This guide has a lot of information, and the Zotero website is packed full of how-tos, but sometimes you may want to look at one of these other library Zotero how-to sites...

Introduction to Zotero Tutorial (Oregon State University) - highly recommended

Advanced Zotero Tutorial (Oregon State University) - highly recommended

Georgia State University - *highly* recommendedl the guide author, Jason Puckett, published a book on Zotero in 2011.

Langsdale Library (U of Baltimore): Zotero

Georgia State University Research Library: Zotero Guide

Zotero for Law Students (Boston College

Getting Started and Installing Zotero University of Michigan

Zotero Baylor University

Zotero - Purdue University