Your site already has RSS feeds included with it — assuming you are using the stock wordpress install. Look in your root folder (or wherever your main wordpress files are) and you’ll see a group of files with names like wp-atom.php, wp-rss2.php and wp-commentsrss.php.
The trick is making sure there are visible links to these feeds somewhere on your site. The url for those feeds vary by feed, but they are usually something like feed://yoursite.com/feed/atom/
.
More information on feeds is available in the Codex.
Some browsers, such as Safari and Firefox, will also “autodiscover” feeds, meaning that if you are viewing a site that has a feed, even if there is no visible link to that feed in the website, a little icon will show up next to the url in the address bar. Most WP themes include the code for autodiscovery in the header file, but just to make sure your’s has it, check out this page.