How to create a text box/comment box in a form

Hi, I am looking to create a text/comment box for a form.  I found some information about how to create a new text area field (through admin -> field management). I added this into the form, but when you go to fill out the form the area is not selectable or editable.  It's just a box on the page. Any advice on how to make this an area a customer can type comments into while filling out a form?