JAVA_HOME is an environment variable which points to the directory where you have installed the Java SDK. You can download the latest version from here(Download). Then install it in the default directory and create an environment variable(Right Click on Computer -> Properties ->Advanced System Settings-> Click on Environment Variables button. Then create a new system environment variable named JAVA_HOME and put its value as the location of your current java sdk installation. )

After this you would need to install Apache Ant(Download), after its installation it should automatically pick up the environment variable. In case you have any further issues I am providing a link which would prove useful. 

Link:  http://ant.apache.org/manual/install.html

If you still face any difficulties, please tell us the exact references you need to include. We'll guide you through the process.