First log into www.office.com with your student credentials. Once you get to the home screen click the One drive icon.
On the Onedrive page there are icons at the top. One of them is called Upload; click it and then select the file or folder you wish to upload. Once your file is uploaded it will show on the list below.
To edit the file, select it and the file will open. Being on the Cloud, the document will automatically save.