variable is a first-step for any application or program that requires JDK to work with. There are many tutorials already provided, but I will try to provide the ones that suffice your needs and are standard based.
Installing the JDK Software and Setting JAVA_HOME
] (From Oracle docs)
How to set java_home on Windows 7
Make sure you select the location where your JDK was installed, because you may install it somewhere else also. Once that has been done you will continue with the installation, should you stumble upon any other dependency problem later.