Moving to subdomain

My blog is currently at http://www.definingdavid.com and I want to move it to http://www.blog.definingdvaid.com. I’m hosted no Dreamhost, and I can’t figure out to do this. I created blog.definingdavid.com and everytime I install WP it says it’s already installed on the server. Is there a way just to pick up everything at http://www.definingdavid.com and move it to blog.definingdavid.com?