Once you have logged in (see here for details on how), you will be presented with the home page of your site.
There are four modes you can be in when logged into your site: Content, Structure, Style & Preview. The Structure and Style modes are used when initially creating the site and as such you won't need to use them.
To identify which mode you are in, look to the top right of your web browser's page. Ideally, you should have the 'A' icon or the 'eye' icon highlighted, as these are the Content and Preview modes respectively. If not, simply click the icon of the mode you wish to enter.
To edit content on an existing page, it's quite simple.
Click on the page you want to edit. Make sure you're in the Content mode mentioned above.
Above the content of your page but underneath the navigation & banner, you will see a small grey button that says "edit page". Click this and a box will appear on your screen.
This is the area where you can input, edit and remove the content of the page you are on. Our system operates on a WYSIWIG editor, that is, What You See Is What You Get. So type away! There's no messy code to sift through here.