Zotero has to be downloaded. It also only works with certain browsers (Firefox, Safari and Chrome). And if you download the Firefox extension instead of the standalone program, you also have to download the plugin to access your Zotero library within your word processor.
You can store your library online, allowing you to access your library from other computers. Zotero is also incredibly easy to use, one click will add most resources to your library. In addition, like other citation software, it allows you to easily cite your collected resources in your paper.
To download Zotero, either the Firefox extension of the standalone version, click here.
If you are using the Zotero FireFox extension, you will need to download the word processor plugin. This page has all the plugins for the various word processors (Microsoft Word, LibreOffice/Open Office) and the various operating systems.
If you are using the standalone version of Zotero, the plug in is available under Tools then Add-ons.
After you have installed the extension, adding resources from most databases is a breeze.
Most journal articles will have this icon appear in the address bar. If you want to multiple resources from a search at once, click the folder icon and select which articles you wish to add.
Similarly, you can add a book to your Zotero library by clicking on the in the address bar of the book's page in the catalog.