In the Firefox plugin version of Zotero, the publication icons now appear by default to the right of the address window, as part of the Zotero 'Z' button.
In the standalone Google Chrome version of Zotero, the publication icons are still located in the browser address window, as they used to be in Firefox (as illustrated in the 'older' Firefox images in the box below this one.)
Add Book Reference to Zotero - Book Icon
Add Article Reference to Zotero - Article Icon
Select Multiple References on a Single Page - Folder Icon
Add Video Reference to Zotero - Video Icon
If a web page does NOT have a Zotero icon in the browser address bar, you can add reference information about the page to Zotero by either:
Drag a PDF file into the Zotero middle column you can have Zotero try to retrieve citation data for the item from Google Scholar or CrossRef by right-clicking on the PDF file and choosing from the menu Retrieve Metadata for PDF