You need to go to your dashboard and then to click on Write and then Pages and create pages that correspond to submit-news, about-us, and contact-us. In the field for “Page slug” (it’s on the right — you may need to click to expand the field) you need to enter those three terms (one for each page, obviously).
You also need to make sure that your Permalinks are set so that the page slugs are used as the address for the page. To do that go to Options then Permalinks and enter /%category%/%postname% in the “custom structure” field.
If you want to have the pages be something other than those page slugs suggest (for example if you want to have an “feed-puppies” page rather than a “submit-news” page) then you can simply edit the header so that it reads /feed-puppies rather than /submit-news.
Similarly if you want one of those links to point to an external site, you edit the link in the header. So you’d look replace everything between the quotes following an href= with a normal url, like http://www.google.com.
So instead of <a href="<?php bloginfo('url'); ?>/about-us"> you’d have <a href="http://www.google.com">.