OK, not sure if you mean Master Profile (your prefilled areas for gallery pic, item details that you keep the same on each listing such as "smoking household" and shipping price etc) OR Seller Details, which is shown after the Description with it's own headers such as Payment, Shipping, About Us, etc.
When creating your listing you must click on the Master Profile dropdown box at the top of the page and load that one. For Seller Details you have to click on the dropdown box to the right of the Template Selection (big blue box).
Clear as mud?
All these areas must be prefilled and saved under your Profiles tab and Seller Details tab. Then when you are creating your listing you can just add them and save yourself alot of typing. If they are already active I don't think you can change them without going the HTML route which I know nothing about
They ARE a little tricky...go to the Help button and view the tutorials. They are a HUGE help.