Trying to add a new widget by moving it from a downloaded plugin.

I'm trying to add a new widget so I can add images (with links into the interior pages of my site). I found a plugin called "Simple Image Widget" - I think it will do what I mentioned above (if not guidance would be appreciated). It indicated on the download instructions to install it as a plugin, which I did. How do I get it from the plugins folder into the widgets window so I can drag it into my sidebars and then create links? Thanks,
John