The sitemap is done for you. The llms.txt is not possible on the Websites and Marketing builder, and there is no workaround worth the time it would take.
Your sitemap
GoDaddy generates one when you publish and serves it at yourdomain.com/sitemap.xml. The address is shown in your SEO settings. Open it once to confirm it lists the pages you expect.
If this check is flagged on your scan it is almost certainly the other half of it: two pages sharing a title, or missing canonical tags. Titles are a per-page setting in the editor, and two pages called Home tell a machine they are the same page.
llms.txt
There is no file manager and no root you can write to, so this one is closed to you. It carries the smallest weight of any check in the scan, and it is the check we are least confident matters, so this is the cheapest thing on the list to lose.
If your screens do not look like this, the wording has moved rather than the setting. Search your platform for the words in bold above. If you still cannot find it, send us the scan link and we will tell you where it is on your setup.