How to enable SEF (Search Engine Friendly) URLs in Joomla! 3.x?
To enable the Search Engine Friendly URLs, go to the Joomla! administrator’s panel. Then go to System > Global Configuration > Site tab > Search Engine Friendly URLs.
Once you enable this option, you have to rename the htaccess.txt file in your Joomla! directory to .htaccess. You can rename the file by using the Site Tools > Site > File Manager.