Well, most blogging software generate an rss feed of posts made automatically. So unless you are using a homemade blogging system, chances are that your rss feed is already out there for people to use. To promote your blog, submit your rss feed to directories, such as syndic8.com
It changed depending on which blog script or servise used. If you use wordpress or joomla, they have their own rss plugins. if you use blogger it is enough to add to your address ( /rss.xml ) ( f.e : yourblog.blogspot.com/rss.xml ) if you wonder whether your service or script have their own rss speciality or not, but you don't know how can you know this, use http://simplepie.org/demo/ to see your site's rss address.
Although I'm new here, I would suggest you gave more information, before some of the guys can help more. For example, Which Blogging Application are you using ? Wordpress or Blogger or another? Ikf we can know the app you use, then there is a good chance to help you further. Regards