They are both correct if you use an electric maker or any yoghurt maker.
If you follow the traditional method, please cool down the milk to lukewarm>add the starter,stir, then allow 30 min, stir again and incubate. Please make sure that you can keep the temperature stable for the next 12-20 hours or until set. You can add a bottle of hot water next to the container with the yoghurt mix and wrap this in thick blanket, towel or something similar.