Screen depicted above is accessible from Settings->XML Sitemap settings. It contains two checkboxes a one text input field. By checking checkbox Post, al posts will be included to sitemap. By checking checkbox Pages, all pages will be included to sitemap. Certain posts and pages can be also excluded from final sitemap. This is what is text field Exclude slugs for. Slugs of pages and posts to be excluded must be written in here as a list separated by commas.
For example, to exclude post hello-world and page sample-page, text field must contain: hello-world, sample-page.
After setting of desired parameters theese settings must be saved by clicking on Save Changes button.
2. Sitemap Generation
Screen depicted above is accessible from XML Sitemap menu item. It contains just one button that allows user to generate xml sitemap by clicking on this button. Button is labeled Generate Sitemap. After submission, sitemap file (or files) is created depending on plugin settings and number of items (<= or > 50000) and message informing about success or problem is shown.