Just to expand a little on what Carol said. That Ship/Pay details thing isn't required but it is nice.
EBay, of course, has the little 500-word blurbs down below your listing where you can put your shipping and/or payment policies. That text is either obtained from what you put in your Shipping and your Checkout profile(s), or else by just maximizing those sections on the lister page and entering it on-the-fly.
The "Create or Modify Shipping and Payment Details" that you are looking at is a different animal altogether, and is actually optional. Say you have some info (doesn't even have to be about shipping or payment) that you use over and over in your listings, and you'd like to put it in without having to keep typing it every time. Do like Carol says, make a S & P profile.
Oddly enough, you won't find the place to create it under the "Profiles" tab. The link's under "Listings", at the bottom of the "Custom Templates" section. You can make more than one: For example, I have one for calculated shipping policies and one for flat-rate policies.
Now, when you create a custom template, or modify one of Auctiva's, you'll see that you can put in a tag for "Shipping and Payment Details". Put that in your template wherever you want that "S & P" info to go. When you make a listing, after you've loaded any other profiles your using (if you are), just select whichever "S & P" profile you made that you want from that little drop down list. It will appear in your listing wherever you put that "Shipping and Payment Details" tag.
Keep in mind, it's optional-- you don't have to bother with it if you don't want to. Not worth losing sleep over. But you'll want to use it eventually because it is a real time-saver.
I know. I takes me a long time to splain things when I can't wave me hands about in the air. One time, me ship was sinkin', and I lost alot a swabbies, because I couldn't 'splain what "abandon ship" was, afore they drowned!
CB