jargonize on "theme directory"

wp 3.4.2 with buddypress 1.6.1 installed installed a GIA video player, it says can't play videos as no flash. maker site says ad this line between head and head tags <?php wp_head(); ?> so looking for i guess the theme directory and/or wp content. and ofcourse the head head tags?

havn't a clue where to look. in themes just let you select a theme, header and editer are greek to me.

thanks