Sort:  

do you have willow trees around you?
if you do, cut some of the young tips of it, boil it and let cool
cut the sweet potato into half and let it soak there for three days
the willow juice will serve as an organic growth hormone kind'a boost
then you can directly plant your sweet potato to the soil and just water 2x a day
good luck anyway .. even if you get to grow them, you will have to grow at least 5 to achieve a huge harvest
that's the annoying part about growing them here
if we were in Spain or in South Italy we'll have more luck

Did you check the video by quinneaker ?
I wanted to plant those slips not a whole fruit.

Yeah, got willow trees.