A Sitemap is a file that contains the structure of your site. It contains all the pages and urls that make up your site.
See the structure of a sitemap.xml file below: On this site (https://www.xml-sitemaps.com/) – You can generate a sitemap for your site by simply stating the url of your site.
Once you have sitemap.xml created, you need to upload it to the server where your site is located.
This done, let Google Search Console know where your sitemap.xml is located by clicking Crawl, Sitemaps.
At this time, just enter the address of sitemap.xml.
Note: If the site above does not generate all the URLs of your site, just copy a line and change to the page that did not come in the file.
If you use WordPress, install the Yoast SEO Plugin as it already creates sitemap.xml for you automatically.
Having the Yoast SEO plugin installed on WordPress and active, you click on SEO in the site administrator area.
Here at this link you can access the location of sitemap.xml. Knowing this, inform the Google Search Console Sitemap.xml