After Updating Google XML Sitemap Do Not Work in Google Webmaster Tools

Hi all, this may seem rather obvious. In the site map submission section of google webmaster, if you have set your site up in webmaster and it is displayed, then when you click on the add/test sitemap, your website address should be displayed??? example https://www.yoursitename.com/ there should be a blank box to the right??? if so you only need to submit the sitemap.xml element of the address, otherwise you will get a 404 error as if you enter the full http address here you are doubling up. So in short if you have your site set up on webmaster you only need to add the sitemap.xml to the page to add or test. Hope this helps. Took me a day to figure it out, so simp,e but not until you see it.