Since the Manifest theme is designed with footer widgets and no sidebar, one way to adjust that would be to move the footer widgets to the right and make them appear as a sidebar. Here is an example of one way you might do it:

body,
#site-wrapper {
	width: 765px;
	position: relative;
	margin: 0 auto;
}
#core-content {
	overflow: hidden;
}
#footer,
#supplementary,
.footer-content {
	width: 235px;
}
#footer {
	position: absolute;
	top: 185px;
	right: 0;
	border-top: none;
	margin-top: 0;
	padding-top: 30px;
}
#supplementary.two .widget-area {
	float: none;
	margin-right: 0;
	text-align: left;
	width: 100%;
}

Note that you will probably need to adjust the numbers in this example to fit your blog.