In order to add a bed note you need to go to Bed View, right click the night where you want to add a bed-night note and click on "Edit Bed-Night Note":
A pop-up window will appear. Here you can type the note and save it:
In order to delete a Bed-Night Note, double-click on it to open Edit window, remove the text and click on Save. If there is no text, the note will disappear from Bed View.