Remember, OneDrive personal is something different. If you haven't saved to OneDrive for Business from Office before, you find it in Other Web Locations.
You see an upload notification while the file is saving, and once it's done, the file is saved in OneDrive for Business.
To co-author a file, open a file at the same time as another person. Any users in the file are listed at the top-right corner. Click a user’s name to see what they are currently editing. Any updates are saved and synced automatically.