You can send Orders Notes directly to your customers if they have provided an email address during the order process.
First go into the Orders table and press on the order you want to manage (I have chosen order #1000003 the latest one for this example).
Once inside the Order, look to the bottom of the centre column.
In here you will find the Order Notes field.
Simply type in your desired note and press Add A Note. This can be a note you want to just leave on the order or a note you would like to send to your customer later.
Your note is now on the order. To send this order note to your customer, simply press on the green button Send Email.
Before your message is sent, a finally confirmation pop-up will appear. If you want to continue, just press OK and your message will go out to your customer.