Good sites with no stupid blocks in robots.txt and no "noindex" meta tags will be indexed automatically anyway. You don't need to do anything, especially if you use a modern Content Management System. If you purchased a very spammy old domain it is possible that Google doesn't like it and because of very hard penalties it may not be picked up. Otherwise, you shouldn't worry, we are 2015 and search engines like Google doesn't need that extra push to list your website in the SERPs. If you worry about the time a new article gets indexed, you can signup for a free Google Search Console account and add your sitemap URL there, so it may help with the index time for each of your new articles.