Adding a "load more/see more" button at the bottom of the category posts widget?

Hello, I use a heavily modified version of dw-focus and would like to be able to add a "load more" type button at the bottom of the categories widgets to load more posts. I can try to do so using the php in the categories where there is "see more" or something. I have no problem editing the php of the widget as I have already done so. If someone could tell me what to add I can do the rest. Thanks!