In the Yesware Contact Sidebar, you can add notes to the "notes" section to save those to the associated Yesware Contact. This will allow you to go in afterwards to edit or delete notes relevant to that specific Contact. This is a great way to keep information on your contacts and have it easily accessible while emailing with them.
In the app site, under the Contact profile you can add notes in the "notes" section. Make sure you click the "save" button on the bottom right to update the notes section.