Header change

Hi! I am new to blogging, so can’t resolve this issue by myself. I have problem with header change. After I am trying to upload a new header picture I get this message ‘Unable to create directory /home/newbaby/public_html/wordpress/wp-content/uploads/2011/04. Is its parent directory writable by the server?’. Are there any other ways to change the header? Can’t find propper instructions on internet…. Thank You