How do I grow potatoes?

I have planted seeds
Now 15cm (6 inches) high,with plenty of green leaves
Apart from keeping moist, do I have to do anyhting else?
How do I know when they are ready to harvest ?

 

Nothing else.
You must wait until leaves are yellow.
Hope you understand me, I never write in English.

 

Wait until the leaves yellow and the fruits are ripe. Then dig them up carefully and let them dry before storing in the dark.

 

I forget:
potatoes don't have to see the light, if they go out of the ground cover them with soil. I think the term is “tucks in.”