To add Jquery in magento we need to add below code in layout file.

/app/design/frontend/package/your theme/layout/page.xml
<reference name="head">
<block type="page/html_head" name="head" as="head">
<action method="addItem">
<type>skin_js</type>
<name>Jquery path with name</name>
</action>
</block>
</reference>