If you are new and want to enable SEO URL’s then you have to follow below point.
System >> Settings then Edit them
Click on Server tab and active SEO URL’s
Create . htaccess file, OpenCart provide default .htaccess file called .htaccess.txt you can rename this file or create new file with below details
Make Apache mod_rewrite turned on.
Now start to add your unique SEO keywords for each products and categories.
Now go and enjoy more traffic and happy customers.