Onedrive is the kind of tool that, once you'll start using it, you can't imagine what it's like not to. It's an easy way to make your files accessible on any computer, phone or tablet, both as a way to send files between devices and back-up these files in case you lose them on your local system.
You can take a picture on your phone one minute, and open it on your tablet the next to edit, then access it on your computer to publish online. You can also continuously and instantaneously share files with friends so they can work on the same project as you. You can even view previous versions of your precious files. It's an invaluable tool.
Anyone with a Microsoft account can access it straight away, and enjoy the 5GB free space (which you can increase with paid plans). It's easy to create a Microsoft account, if you don't have one. Then you can access OneDrive at onedrive.live.com, where you can drag and drop files to and from your desktop or browser.
However, to get the most from it, it's best to properly install OneDrive on your PC, smartphone, tablet, so you can always find your files quickly and easily.