For general use, the best method for adding items to Zotero is to use the Zotero Connector button in your web browser. See For information on using Zotero's import functions to add items to your library, see the Getting Stuff into Your Library for more information on this and other methods.

For troubleshooting import and export issues, you can try the relevant steps in the translator troubleshooting procedure and direct questions to the Zotero forums.