First, go to settings > privacy and make sure that the top option is selected (visible to everyone including search engines).
WordPress automatically pings search engines when you publish new posts, so they will get to you in a little. It can take up to 6 weeks for someone to be indexed although it is typically much quicker. You can shortcut the process a little by getting a google webmaster account and then verifying your blog with google: http://support.wordpress.com/verifying-with-google-webmaster-tools/ .
The same procedure can be used with Bing and is virtually identical.