CCMathHammer is a Java application, and thefore you must have a Jave Runtime Environment installed. I'm sure you do already. This program require Java 1.6 (or Java 6 or whatever they're calling it now), so if you try to run this and it fails, then try upgrading your Java. If you don't have Java or are having problems, GO HERE to install or upgrade.
I've developed this under Windows with Java 1.6.something, so that's where it will run optimally, but it's also been run under Mac OSX.something with success. I think there was a font sizing issue, but it was totally functional. Just resize the window a little to see everything. If you have any problems with it, send me an email with a screenshot of what you're seeing, and what OS and Java version you're running ('> java -version' to get the version) and I'll see about fixing it.
Ok, ok, ok...
In windows, unzip the file into any directory, and double-click the run.bat.
In Mac/Linux, unzip the file into any directory, and run the run.sh. Failing that (execute permissions prolly aren't set properly, stupid windows), from the cli:
> java -jar Mathhammer.jar