Create the Main Class

Create a new class in your mod package that implements MModdingModInitializer:

MModdingExempleMod.java

public class MModdingExempleMod implements MModdingModInitializer {

    public static MModdingModContainer mod;
    
    @Override
    public List<ElementsInitializer> getElementsInitializers() {
        List<ElementsInitializer> elementsInitializers = new ArrayList<>();
        // Check the "Use ElementsInitializer" page
        return elementsInitializers;
    }
    
    @Override
    public void onInitialize(ModContainer mod) {
        MModdingModInitializer.super.onInitialize();
        MModdingExempleMod.mod = MModdingModContainer.from(mod);
        
        // Your amazing code here
    }
}

You must replace MModdingExempleMod by your mod's name!