installing a screensaver

I am trying to figure out how to install a screensaver because I seem to have no idea how to do so. I downloaded the file and tried to set it up via the system preferences page. But when I try to choose the file, it shows up grey and won't let me select it. When I do a "get info" it says the file is a "unix executable file." I pretty much have no idea what to do, so any help is appreciated.

Thanks.