When syncing with OneDrive, Joplin creates a sub-directory in OneDrive, in /Apps/Joplin and reads/writes the notes and notebooks in it. The application does not have access to anything outside this directory.
In the desktop application or mobile application, select "OneDrive" as the synchronisation target in the Configuration screen. Then, to initiate the synchronisation process, click on the "Synchronise" button in the sidebar and follow the instructions.
In the terminal application, to initiate the synchronisation process, type
:sync. You will be asked to follow a link to authorise the application (simply input your Microsoft credentials - you do not need to register with OneDrive).