Hi Lillie,
try to make a search on heritage sweet onion in this forum.
Sören.

Here are the planting instructions, etc for Heritage Sweet White Onions. These are topsetters and mature one to several bulbs in the ground also. They do very well here and are good for scallions and mature bulbs for cooking or pickleing.

Our multiplier onion sets should be planted 1 inch
deep 4 to 6 inches apart. If you wish to increase the
white section of the plant for harvesting as table
scallions, the soil should be mounded around them as
they grow to a depth of about 3 or 4 inches.
In mid summer, the leaves will begin to die back from
the tips and start to fall over with top sets on the
stalks. At this time you should stop watering. Within
a few weeks, the bulb lets or sets will be ready for
harvesting. Dig them after the leaves have turned
yellow and brown and remove the top sets and replant.
Do not cut the stems at this time. Let them cure in a
warm dry spot until totally dry and the outer skin of
the bulb has turned to a papery feeling. At this time,
the stems can be removed to within one inch of the
bulb and the onions can now be stored in a cool dry
place at 34 F or grater for eating or planting.
(from original planting directions)