Edit shared notes on iCloud.com
You can edit shared notes. Everyone you add sees any changes made to the note.
In Notes on iCloud.com, do one of the following:
If you are the owner: select the note in your notes list.
If you accepted the invitation to the shared note: select the note in your notes list.
If you have been invited to edit a note but have not accepted the invitation: click the link you received, then click Open in Notes.
After you open the note for the first time, it appears in your notes list on iCloud.com.
Edit the note.
When someone edits a shared note, everyone sharing the note sees the changes, but no one can see who made them. The timestamp below the note in the notes list shows the last time it was edited. If you are not currently editing a shared note, a yellow dot appears next to the note in the notes list when someone else edits it.
If you are invited using an email address or phone number that is not associated with the Apple ID you use for iCloud, ask the owner to re-send the invitation using the correct email address or phone number. You can also follow the onscreen instructions to associate that email address or phone number with your Apple ID.