main.css at ~ line 309
change
padding:23px 30px 0 290px;
to
padding:23px 210px 0 290px;
for #center-main
in customer/home.tpl add <div id="right-bar">My right bar content</div>
after
<div id="left-bar">
....(left-bart content)
</div>
CSS for right-bar presents in your main.css so it would be 158px in width