Zotero is a bibliographic manager, which means that it will collect the bibliographic information about your sources and store pdfs as well. Once you start writing your paper, you can use Zotero to insert references and to create and format your bibliography. Learn how to download Zotero and customize it for NMU here and here.
Don’t feel up to downloading anything right now? Microsoft Word can also collect references and create citations and a bibliography for you (it can’t save your pdfs, though). Learn how to use Microsoft Word for this purpose here.