In addition to having notes on citations (e.g. books, journals, etc.) you can also have freestanding notes on a reading lists. For example you might add a comment at the top of a list stating how you expect your student to approach/utilise the reading list.
To add a freestanding note to a reading list icon on the Add icon (top-left on toolbar) and then select “Note” from the popup window that appears. Now enter the text of your note in the box provided and click on Save (bottom-left of popup window) when finished.