Depending on the type of team you select when creating your team, the General channel may already have a OneNote notebook. However, if a OneNote notebook is not automatically created for your team or a OneNote notebook is desired for a different channel, one can be added.
Select the plus sign (+) at the top of the channel.
Select OneNote from the list of apps.
Name the notebook and select Save.
The plan tab will appear at the top of the channel.