Ensure that you have the JRE installed. This can be downloaded from http://java.sun.com/j2se/. You must ensure that you use at least Java 7, as FlowframTk does not work with earlier versions.
To install, download the installer flowframtk-0.8.4-installer.jar and run it. This can be done from a terminal or command prompt using:
java -jar flowframtk-0.8.4-installer.jarDepending on the setup of your operating system, you may also be able to double-click on the .jar file to run it.