To add a source, click   icon. For different webpages, it will change its appearance to match the source type. For example, and.

One of the reasons Zotero is a powerful tool is its ability to recognize and gather bibliographic data from many different sources on the web. This is done through what the developers refer to as translators. When doing research in an article database or library catalog, Zotero will use different translators to store information it needs to organize items and make citations. To see available translators for a specific webpage, right click the icon. 

Zotero has been designed to work well with most library catalogs, research databases, many major publisher's websites, as well as some commonly cited news sources. When a specific translator is not available, Zotero will attempt to use the webpages metadata to gather the necessary information, but the results are not always perfect. You can edit the bibliographic data for any item in your library at any time.

Zotero also allows the user to add items manually. This is sometimes necessary in the case of Zotero incorrectly pulling bibliographic data about the source from certain websites, or when you are citing something not represented on the internet (an interview, archival item, etc.).

To manually add a source, click the plus sign button in the Zotero window. 

Choosing the source type will create a new source, and will display a window with blank fields for you to fill in.

Zotero can utilize an item's identifiers if they have been assigned one. The identifiers Zotero will work with are ISBNs, DOIs, and PubMed IDs. If an identifier is recognized by Zotero on the webpage from where you are trying to add an item, it will usually show up as an available "translator". You can also add an item directly using its identifier.

Click the icon that looks like a magic wand, and enter in the DOI, ISBN, or PubMed ID number.