try something like this.
@Mod.EventBusSubscriber(modid="yourmodid", bus= Mod.EventBusSubscriber.Bus.FORGE)
public class EventForge
{
public static final ResourceLocation DIMENSION_TYPE_RL = new ResourceLocation("yourmodid", "yourdimension");
@SubscribeEvent
public static void onRegisterDimensionsEvent(RegisterDimensionsEvent event)
{
DimensionManager.registerDimension(DIMENSION_TYPE_RL, DIMENSION, null, false);
}
}