Zotero will accurately import the reference information on a Web page, but the supplied reference information may not be fully accurate.
When you have selected an item in the center pane, you can view and edit its bibliographic information via the Info tab of the right-hand pane. Most fields can be clicked and edited. Changes are saved automatically as they are made.
You can add files as attachments to existing Zotero items by right-clicking on the Zotero item and choosing “Add Attachment” or clicking the paperclip icon in the Zotero toolbar.