We have created User Generator module to help you to randomly generate as much members as you want. User Generator allow you to generate up to 5,000 (5K) users with photos and predefined settings with a single click. You do not need to register user manually, you can get thousands in few clicks. This is an addon to kickstart your community.
Sitemap is a tool that inform search engines about the structure of your site. By placing a sitemap on your website, you enable Search Engine crawlers (like Google) to find out what pages are present and which have recently changed, and to crawl your site accordingly. You don't have to manually submit sitemap as it automatically (if settings is enabled in the admincp) Notify Popular Search Engines (Google, Bing) when sitemap changes.