The Post it notes panel is displayed as a docked tab:

The number of outstanding post-it notes (sent by colleagues) is shown also.
Hovering or clicking on this tab exposes the list of post-it notes:

The list shows the date/time when the post-it note originated, the sender and the message.
Double click on the post-it note to open.
The buttons are as follows:

• Reply: Send a reply to the sender
• Snooze: Turn off the reminder for a period of time
• Contact: Open the contact form linked in the note
• Clear: Turn off the reminder permanently and mark as completed