One way is with a CSS Insert. Look at the source of the page and locate the widget. For example you might see this
HTML Code:
<div id="polls" class="widget widget_polls"><div class="widget-title"><h3>Polls</h3></div>
In this case you would use the following CSS Insert
HTML Code:
div#polls h3 {
margin-left: 20px;
}
where 'polls' would be the widget ID in question and you would adjust the 20px to what ever you want.