After you post an article your blog automatically pings several websites to inform them that you have new content . Make sure that you have Blog visibility On so that search engines can crawl your page. And don't forget to add a sitemap and you'll be fine. I think that you can find a special plugin to ping more sites when you post but i don't think that it is necessary .
Ping to get indexed quicker! You can use websites like Ping-O-Matic to send pings to multiple websites at once. You can use FeedBurner's ping service as well.
Pinging a blog after you post new content/updates is like giving a signal to the SE spiders to crawl your site and to get indexed faster. I use autopinger and pingoat on my blogs.