By default, Squarespace will create a sitemap for you, which you can access at URL: /sitemap.xml.
Suppose your site is: example.squarespace.com (or example.com) then you can access the sitemap with the URL: example.squarespace.com/sitemap.xml (or example.com/sitemap.xml).
Squarespace will show a page like this.
After you have published your site, you can submit the sitemap to Google Search Console.
wait a bit
Done
You will see the result here
You can see the status of pages that have been indexed by Google (ie pages that have been displayed on Google Search Results) and pages that have not been indexed.
