After adding PrimeFaces to your JSF project, you can start using it in your pages using the namespace:
xmlns:p="http://primefaces.org/ui"
or, for PrimeFaces Mobile:
xmlns:p="http://primefaces.org/mobile"
This example should render a spinner:
<html xmlns="http://www.w3.org/1999/xhtml"
xmlns:h="http://java.sun.com/jsf/html"
xmlns:f="http://java.sun.com/jsf/core"
xmlns:p="http://primefaces.org/ui">
<h:head>
</h:head>
<h:body>
<p:spinner />
</h:body>
</html>