How do I add bullets on the Recent posts list?

I think it depends on your style sheet.
Try to assign class to your list tag and create css rule for that class

html:
<ul class="test">
<li>item1</li>
<li>item2</li>
</ul>

css:
ul.test{
 list-style: disc;
}

I think your theme style sheet, it locates in
wp-content/theme/(your activated theme)/style.css

Could you tell me your web page url ?

open style.css locate at
http://www.oxbargain.com/wp-content/theme/mk3/style.css

and add this line

li.widget_recent_entries ul{
 list-style: disc;
}

sorry, let’s try

#content .products .widgetcase ul li.widget_recent_entries ul{
 list-style: disc;
}

You’re welcome.