Hi Ut Det,
In order to use the seller details sections when listing through Auctiva, you will first need to create a seller details profile within your account, which can be done by clicking the "Seller Details" link under the "Profiles" tab within your account. When creating your seller details profile, you will have the option to enter the text you would like to appear under the Shipping, Payment, Terms of Sale, Contact Us, and About Us sections.
Once you have created a seller details profile, you can apply that seller details profile to your listings by selecting it from the "Select Seller Details" drop-down menu on the Auctiva listing creation page, which is just to the right of the "Select Template" button. When you select your seller details profile for a listing, the information stored within in will appear under the appropriate headers within the template.
If you have any additional questions or concerns, please feel free to contact our customer support team by completing the web form on the following page of our site: http://www.auctiva.com/help/requesthelp.aspx
-Mike