There are several ways to add references to Zotero:
To export your EndNote library for use in Zotero, click "File" and then "Export." Set the output style to "RefMan (RIS) Export" and save it as a text file.
In Zotero, click the button that looks like a gear and choose "Import." Just double-click the file you exported from EndNote. The new references will be added to a collection named "Imported" followed by the date and time.
Note: The RIS output style provided by EndNote does not include File Attachments for Journal Article entries during export. If you want Zotero to import file attachments, please see detailed instructions from Zotero.org.
This is Zotero's three-column interface. References show up in the middle column. Details of a highlighted reference appear in the right-hand column. Create folders to organize references in the left-hand column.
Using the Firefox Zotero add-on, you will see a yellow folder in the status bar of your browser when you search PubMed using the Firefox broswer. Click on the yellow folder icon in the address bar. This will open up a popup window. Zotero recognizes the citations from your PubMed search. Select the citations you wish to download in the window and then click "OK." Your citations will be added to your Zotero Library.