TOPing an auto is a bit trickier than regular weed. It needs to be done not too late, or the plant will start flowering. The best time is to do it, removing the 5th node. If you do it too early the root system will be too small, which will make the plant take longer to recover.
You top it at the third node, but if you are on your first grow its better if you don't top, just grow it as it is, and get a grasp on how to read the plant first.
Congrats on the leaves ππ
Good luck growmie (grower + homie, just so you know)