Export D2L gradebook
You don't have to do anything with the file: it can be pulled into Excel and modified, but you should save a copy somewhere with your course folder or class records. It is recommended to do this occasionally throughout the semester. (Also, if it is during a semester and you are thinking you want to change/delete grade items, you ALWAYS want to Export the Gradebook out first, so you can resurrect things if needed.)
Consider saving the data in your course Gradebook in an EXPORTED file.
Link is to a video demonstration (no audio) of how to export D2L gradebook data to an EXCEL file, and then taking that newly created file from the laptop's DOWNLOADS folder and putting a copy in the users ONEDRIVE account, in a folder named "2017 Nanoscience".