Keywords for my site without plugin

Hello!

I want to ask you how and where to set the general keywords for my site.

Which code i have to use?
Now i have add the bellow code and works only for the keywords of the post. How to change it to show and the keywords of my site?

<meta name=”keywords” content=”<?php if(get_post_meta($post->ID, “keywords”, true) != ”) echo get_post_meta($post->ID, “keywords”, true); else echo strtolower(get_bloginfo(‘description’));?>” />