You go into 'edit entry' this should allow you to edit any part including the title?

If you want to rename the entire blog (and not just the entry) you should go to "my settings", then click the layouts and blogs tab, and then click the name of the blog (which is just beneath "Your current blog" and just to the left of the "post new entry" link - it looks like one link but is in fact two!). You can then edit the name of the blog.