Creating a Collection - http://support.proquest.com/refworks3/apex/homepage?id=kA140000000GwFJCA0&l=en_US
RefWorks enables you to organize your references into folders and subfolders, making it easier for you to manage all your citations over the course of different projects.
Brief video tutorial:
Using the drag and drop option: Tip: If you want to add your documents to a specific collection, make sure you’re viewing the collection first.