Are they already rooted or just slips ? Not that it makes much difference ! Slips just take a while longer to start growing ! If you can grow regular white potatoes just copy that for the sweets ! Good loose soil and fertilizer ! Sweet potato tops run so spacing at least 3 feet apart ! You can also eat the tops ! They take longer to mature than whites so check the variety for approx harvest time ! When you harvest sweet potatoes they have to cure a while to develop their sweet flavor ! So do not just dig and eat right then ! Refer back to the variety you are growing to see how long they recommend ! Here in the US it is common to let them lay on top of the soil and get a light frost before eating !
Next time you want to plant sweet potatoes just buy one from a garden stand or any organic gardener and stick it in the soil and water it ! You will have more slips than you can plant ! You can plant the slips as they are and they will take root with moderate water or stick them in a jar and add water and they will develop roots,, then plant !
They root easily ! One year I stuck a sweet potato in a horse manure pile that was left over from the garden ! I had more slips than I could count ! Generally here they are planted late in the season so harvest time is in cool weather !