How to add an external javascript/css file to Magento?

<action method="addJs"><script>js/yourfile.js</script></action>
<action method="addCss"><stylesheet>css/yourstyle.css</stylesheet></action>
OR
<action method="addItem"><type>skin_js</type><name>js/ yourfile.js</name></action>
<action method="addItem"><type>skin_css</type><name>css/yourstyle. css</name></action>