LinkedIn SlideShare is an online platform that allows users to upload and share presentations in various file formats such as PowerPoint, PDF, and Keynote. To create a SlideShare presentation, a user first needs to log into their SlideShare account or create a new one if they don't have one. They then design and gather content for their presentation using Microsoft PowerPoint. Finally, they upload the completed presentation file to SlideShare, add a description and categories, and publish it.