Download and install a recent Java SE Development Kit (Java SE JDK) or OpenJDK.Please note: You'll need a full Java Development Kit (JDK), a simple Java Runtime Environment (JRE) won't work.
Check your environment-variables: JAVA_HOME needs to point to the root-directory of your JDK.
Choose a name, login and password for the administration account. The password must contain at minimum 8 characters with mixed case, digits and symbols.
Now you're redirected to the login-page. Enter the login and password for the newly created administrator.