To update your website you will need to login to the dashboard to make the changes. You can approve or delete comments, add new pages, posts and install some really cool plugins to make your site more powerful. Go to http://yourdomain.com/wp-admin/ and enter your WordPress user name and password. This is how your dashboard should look like.
Now go to Settings and click General. Go through the settings and change it for your site needs. There is one part I would like to highlight, that is the Permalinks page. Go to Settings > Permalinks and click it. Select Custom Structure and enter /%category%/%postname%/. This will give your a very pretty url for all your pages like this http://yourdomain.com/categoy/postname. Also it will make your link SEO friendly and bring in more traffic for your site. So I highly recommend you to change that.