A couple months ago I put a regular storebought sweet potato in a cup of water. I've continued to keep it full of water & in a sunny location. Below you will see my Sweet Potato Man is doing great!
I recently cut a couple of the sweet potato starts from the top of my Sweet Potato Man & put them directly into some potting soil in a 5 gallon pot (pictured below). I also put a couple starts in my backyard garden.
UPDATE: Here is what the same sweet potato starts looked like come July: