Add a reference manually

While you should generally avoid adding references manually, it can be useful for adding primary documents that aren't available online. References can be added manually by clicking the green New Item button in the Zotero toolbar and selecting the appropriate reference type:

Data about the reference can then be added by hand in the right-hand pane.

The option "Web page" is not available in the New Item menu, but it is possible to create another reference type and then change to Web Page in the right-hand menu. The reason for this is that it is much easier to use the Zotero Connector to save a web page rather than creating the reference from scratch.

Add from DOI or ISBN

You can also add a reference from a DOI or ISBN. Click the wand in the top menu:

Type your ISBN, DOI or other identifier, and click Enter.

Add a reference from a PDF

Have the Zotero app window open
Find the folder with the PDF (or any file) on your computer
Drag the PDF to My Library
Zotero will automatically create a reference and add the PDF as an attachment