To create rss feed for you Joomla 3.x site, you dont need to install any 3rd party extension or plugin. Simple add
?format=feed&type=rss at the end of your blog page url
for example your joomla site url is http://myjoomla3xsite.ext/blog.html then the RSS feed will read as

http://myjoomla3xsite.ext/blog.html?format=feed&type=rss

If under Global Configuration > Site > SEO Settings > Search Engine Friendly URLs = No

then add &format=feed&type=rss at the end of URL, for example

http://www.myjoomlasite.ext/index.php?option=com_content&view=category&layout=blog&id=1&Itemid=123

will become

http://www.myjoomlasite.ext/index.php?option=com_content&view=category&layout=blog&id=1&Itemid=123&format=feed&type=rss

NOTE : This will work for Menu items of type Category Blog