With this CSS:
#page_footer {
height: 214px;
clear: both;
background: url('images/footerbg.jpg') top left no-repeat;
position: fixed;
bottom: 0;
left: 0;
width:100%;
}
The last 4 items are added. You may want to adjust the left and width.
To discover what CSS is output by your theme, use a web inspection tool such as Firebug: http://getfirebug.com/ , Chrome Inspect Element: https://developers.google.com/chrome-developer-tools/ or Internet Explorer 9+ F12 Dev. Tools: http://msdn.microsoft.com/en-us/library/dd565627(v=vs.85).aspx#csstool
There are others.
When editing CSS, use a Child Theme
http://codex.wordpress.org/Child_Themes
Custom CSS Plugin, or Theme provided custom CSS option.
Edits to parent themes are lost on theme update.
Learn CSS: http://www.w3schools.com/css/