Workflow Messages
You can setup the message feature by click on the Design drop down > Click on Workflow > Click on Messages.
Item Messages:
If you want the customer to be able to include a message such as special instructions click the check box next to this box and write a short message for the customer to see.
Order Messages:
If you want the customer to be able to include a message at the end of the ordering process; such as special delivery instructions, click the check box next to this box and write a short message for the customer to see.
To save your changes click the Next button.