Open IntelliJ and click New Project. Set the language to Java and pick the JDK you installed earlier. If IntelliJ doesn't detect it, click Add JDK and browse to your JDK installation folder.
Give your project a name like JavaPractice and choose a location on your machine. Leave the build system set to IntelliJ (not Maven or Gradle for now).
Once the project opens, you'll see a src folder in the left panel. Right-click src, choose New > Java Class, and name it HelloWorld. IntelliJ creates the file with a class declaration already written.
Type your main method inside the class. IntelliJ offers a shortcut: type psvm and press Tab. It expands to the full public static void main(String[] args) signature.