A Wordpress SEO plugin. The two most popular ones are All-In-One-SEO and Yoast SEO. It is a toss-up as to which is better, but as a small local business owner wishing to start with basic SEO, and later upgrade to something more sophisticated designed specifically for local SEO, then Yoast SEO is your best bet. Its basic offering is free and designed for any website. But, you can later upgrade to Yoast's Local SEO plugin which additional features for local businesses.
You can download it from here:
After activating it, make the basic settings in the Settings section. In the process, the plugin will create the XML sitemaps for your site which Google expects to see.
To check to make sure it was created, add "/sitemap_index.xml" or "/sitemap.xml" to the end of your URL. So, if your URL is https://mynewwebsite.com type in https://mynewwebsite.com/ or https://mynewwebsite.com/sitemap.xlm. You sitemaps should display.
If you want to double check, you can use a XML site validation tool, such as the one at:
One tip: Don't be too concerned about the "Readability" score the plugin provides. It doesn't really work that well. (But, everything else does!).