You can choose to disable Sitemaps and RSS by clicking on the cog icon on the right side of the site header bar, and selecting Settings.
From here, click on "General" in the left sidebar and navigate to "RSS and Sitemaps" near the bottom of the page.
You can choose whether to disable Sitemap RSS and XML in the first line of this setting. On the second line you can choose whether you want to disable RSS within categories and on the site itself. We recommend that both of these settings be enabled unless you do not wish to allow your content to be aggregated by external sources. If you choose not to enable these settings remove the checkmarks and click "Save" at the bottom of the page.