Optimize a PHPbb based site for SEO?

Hey everyone
Hope someone can help. I'm trying to figure out how to optimize my phpBB based website for SEO. I've put my keywords in the title, website description, and meta tags. Google webmaster tools is showing me my top keyswords areL: users, phpbb, board, total and posts.
How can I fix this? Thanks!

To set the meta tags, you have to go to your current theme and edit your overall_header.html file.