<p>I don't have any experience with clickers, but from what I've been told, all they do is act as another "keyboard" on your computer, and emit specific key signals (like "down" or "page down").</p>
<p>I suggest two things:</p>
Firstly, make sure OpenLP is selected, and not PowerPoint, and try clicking. See if that works.
Secondly, find out what keys your clicker emits, I would assume that the manual that came with the clicker would tell you what they are.