Downloadable JAR file: Click here to download the Visual X-Toy jar file. Your browser may prompt you to run this application, or it may save it to your downloads folder. In the latter case, double click the toy_1.5.jar icon in Finder/Explorer to run Visual X-Toy. You can save toy_1.5.jar to a location of your choice to run in future without re-downloading.
Mac Users: You may need to allow apps downloaded from "Anywhere" under Security & Privacy in your system preferences. (Alternatively, after you attempt to run the .jar file, you may be able to specifically authorize "toy_1.5.jar" to run in the Security & Privacy preferences.) You may also be prompted to download and install the latest version of the Java Runtime Environment from Oracle. You should do this even though you already have Java installed on your system in one form or another. It won't break any existing programs.
Windows Users: If you have trouble running .jar files, please follow the instructions in this Microsoft web forum thread to associate .jar files with Java properly.