Hi margied66!
Welcome! I'm relatively new myself, so don't feel like the lone ranger! There are many of us "Newbies" around here.
The community here is really helpful and so eager to assist others! Everyone is so patient and encouraging!
Even those that are proficient on computers, selling, and this site have not forgotten that they too were beginners at some point; they graciously assist us "Newbies" with open welcoming arms!
So ask away; anything and everything as others of us probably have the same questions.
I've posted a few times, and have learned a few helpful hints;
1. On your new listing scroll down to "Shipping" > on the left you'll see maximize > click to maximize > scroll down to see either flat rate, calculated, or pick up > when you check calculated, areas for completion appear; dimensions, weight, etc.
(I have never used the calculated shipping as I didn't venture to look for, &/or try it, so thank you for the question as I learned something new!)
2. If you want to add item specifics there are 2 links under the category selection area; 1 has either New or Used options only; the other has a Custom Area; you can write your own descriptions or information.
*** If try to post your listing, but it doesn't go through, check the scheduled listing area...if it shows an error, then your Custom Item Specifics are probably too long/too many letters. Even though you can type quite a bit into the item specifics areas, keep it short and to the point as too many letters will prevent listing to load onto ebay. Edit your listing from that same area and try to repost or reschedule. I'd try to post a few to get the hang of it before scheduling any just so that you aren't caught unaware if they don't go through.
3. BIG HINT: I was having a terrible problem with font type, size and even color changing even in the middle of a line or paragraph when I'd go back for review; both seller specifics and descriptions.
Jeff CEO taught me about "Cookies" with multiple revisions, plus "Cut/paste" from outside Auctiva can cause havoc; both can drive a normal person nuts!
I often have to delete these "Cookies" to get things to "Stick" as I'd like them to be. Also, sometimes you might try using notepad vs Word to copy from, and even then it can cause problems. So PREVIEW before posting.
4. She's right about your feedback, etc showing up later on the actual listing. Note the same is true of your return policy. Although the payment section shows in the Auctiva preview, the return section won't show up in the preview; only on the actual listing. You can make a Master Checkout/Return Policy too under Profiles too.
And ask away, so that we all learn and grow together! Everyone is so nice and helpful!