how set metatags for facebook Social Plugins

hi everybody,
if you want to display an special image and description in users pinwall, when he clicked "like",
you have to set metatags to let facebook know, what is to display on the pinwall
the metatags must placed on the site where the like-button is . . .

the metatags are looking like that:
<meta property="og:title" content="Threat" />
<meta property="og:type" content="non_profit" />
<meta property="og:url" content="" />
<meta property="og:image" content="" />
<meta property="og:site_name" content="Plugin Development" />
<meta property="fb:admins" content="2525255225512" />

i am in trouble, because i don't figure out, how to place the metatags on the site in elgg 1.8

who can help me?

nice greetings from cologne/germany