The simplest way to add items to Zotero is to use a Web Browser Connector (install instructions).
When you find a source you would like to save, click on the connector button. You will see a pop-up indicating that Zotero is saving your citation.
Note: depending on your browser, the button may be in a different place.
If you have an item in front of you and you can't find a record for it online, you can create a new citation manually. First, click on the green plus sign icon and choose the type of source you want to create a citation for from the drop-down menu.
Next, fill in the fields in the new citation you have just created.
To edit existing citations, just highlight the individual reference you wish to edit, select the field wish to add to edit, and type in your changes.
If you have a book's ISBN, an online article's DOI or PMID number, just click the magic wand button: "Add item by identifier." Type in the book or article's number, and Zotero will automatically download its information and save it to your library.
Comprehensive support and documentation is available at Zotero.org. Check out the following support pages for help Collecting Items: