Modify HTML template for widget/plugin

I’m new to WP and it’s a lot more confusing than blogger. Sorry for the n00b question below.

I installed LinkWithin and my partner wanted to customize the text that appears above the widget. LinkWithin FAQ has simple instructions, maybe to simple:

Modify your HTML template to include the code below:

<script>linkwithin_text=’Your custom text:'</script>

I’m not sure where to find the HTML template to modify it exactly. I would think this script above would be somewhere in the php for the plugin found under Plugins>Editor>linkwithin/linkwithin.php. Is this the right place to be looking?

I did not find it there or anywhere to modify it. I then thought, maybe they want me to just drop the above script anywhere in there. I stuck it at the bottom of the linkwithin.php. That worked for me but not for others, it got real buggy and made the whole blog freak out. We had to remove it.

If there is text already that appears above the widget, it only makes senses to edit that text in the code to what I want and not add a script to override it. Some help finding said text would be very helpful or better instructions where to place the script or maybe a better plugin that is more customizable.

Thanks in advance.