Access notes outside of Microsoft Teams
In Teams, go to your OneNote tab, click Open in OneNote, and then select either Open in OneNote (for the desktop app) or Open in OneNote for the web.
You can also open your notebook directly in OneDrive for Business or SharePoint.
You can open your notebooks from the OneNote app directly in OneDrive for Business.
To open OneNote in Teams, tap Tabs from a team channel and then tap OneNote.