How do I let search engines know about my Sitemap?

To do it Ц register your website in webmaster services, provided by search engines (for example: for Google or for Yandex). After registration, you will be able to submit Sitemaps directly in your account.
Another common way Ц include in robots.txt the following line:
Sitemap: http://website.tld/mysitemapfile.xml
If you need to provide several Sitemaps, please add the same line for each file:
Sitemap: http://website.tld/mysitemapfile1.xml
Sitemap: http://website.tld/mysitemapfile2.xml
Sitemap: http://website.tld/mysitemapfile3.xml