Hi Hasbeans
You plant the slips (shoots) rather than the whole sweet potato, unlike regular potatoes. The shoots will root in water, so 1 potato will give you a few plants.
I grew some outside about 5 years ago they were lovely attractive plants, however I got a bunch of spindly carrots as the end result and the little slugs had nibbled them all over.
I would recommend a little cloche tunnel, plenty of feed and some organic slug pellets