I am new to WordPress and downloaded the 3.5.1 version from my hosting provider. I want to add www in front of my domain and I read from many sources how to do this. Go to settings then general and change it there. Thats fine except my screen in General looks nothing like the instructions I have been following
It does not have a place to change the Site or WordPress URL. Am I missing something
You are in the wrong settings page. Your site is a multi-site setup; the URL is set in the site manager, not in individual sites.
Go to Network Admin/Sites in the My Sites menu:
Select a site to edit:
Change the URL:
You need a subdomain setup to get editable URLs.
See Create A Network for the installation guide and Configuring Wildcard Subdomains for the server setup.
It looks like your hosting provider auto-installs a modified version of WordPress.
You should consult them, or remove this install entirely, and do a manual install in its place.
EDIT: I defer to Toscho.
it looks like you are using a wordpress website hosted on wordpress.com. The tutorials your are following are for the wordpress you download and install it yourself.