Upfront theme – blog post excerpt

I've set up a blog page and have dragged the "Posts" element over. How do I change the "content"? At the moment it says "Please type your content here" and I can't see how to change it – ideally it would pull through some content from the actual blog article that's written but no matter what I click on I can't get it to do what I want it to. Also how do I change the arrow "read more" to actually say "read more"