Select the document you want to edit in OneDrive.
You can choose to make quick changes (Edit in Word Online) or use all the features of the Word application (Edit in Word).
Once you have selected a document, click on the three dots next to the document name. Select "Open" and from there the option of whichever one you want to edit the document in.
Click on the File- tab and select "Save As". You can now select the "Rename"- option and enter a new name in the text box.
Rename can also be done directly from the document. Move the cursor over the name of the document and right click on the field. You can then rename the document.