Comments field at checkout

I want to add a text area box at check out for the customer to include a message. I can't find this in the forum or documentation. Is this possible?

Thanks

I've done this on my site using business edition customers can add comments at checkout.

I created a custom field in Display > custom field and create a new field

Select the "order" table and field type "text" or Text box" and check boxes to show on front end and back end.

New field will be there on checkout.