For Windows:
Download and install Java 8 from Oracle:
Windows Java SE Java 8 for 32 bits or Java 8 for 64 bits
After you have installed Java 8 in your machine, double click ExplotPack.jar or from a console run this command: "java -jar ExploitPack.jar"

For Linux:
Under any Linux distribution that supports DEB packages like Ubuntu, Debian, Kali, etc. you can run the following commands to install Java 8 from an official repository
Copy and paste the following in a terminal window:

echo "deb http://ppa.launchpad.net/webupd8team/java/ubuntu trusty main" >> /etc/apt/sources.list
echo "deb-src http://ppa.launchpad.net/webupd8team/java/ubuntu precise main" >> /etc/apt/sources.list
sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys EEA14886
sudo apt-get update
sudo apt-get install oracle-java8-installer