You'll need to provide more info for us to help @thisandthatheaven because there are different versions of the listing form and, possibly, you may have inadvertently opted into business policies.
As a brand new seller I'd first suggest opting out of biz policies if you're using them. I personally prefer them, but if you're new to shipping it may not be right for you.
Manage and edit them or opt out of using them on this page.
After you work out whether or not you're using biz policies, go into a listing draft, scroll down to shipping, then take a screenshot you can post here and let us know where/how you're getting stuck.
