Like any seeds, keep them in a cool dry place until you repalnt them in the spring. Make sure it is also rodent-proof because mice love to eat these seeds. Not sure what you mean by wild sunflowers but everything is owned by someone so be sure to have the permission from the landowner before you harvest any seeds from "wild" plants. Watch the plants until they start to dry and then harvest the seeds or cut a few stalks to dry at home.
Like any seeds, keep them in a cool dry place until you repalnt them in the spring. Make sure it is also rodent-proof because mice love to eat these seeds. Not sure what you mean by wild sunflowers but everything is owned by someone so be sure to have the permission from the landowner before you harvest any seeds from "wild" plants. Watch the plants until they start to dry and then harvest the seeds or cut a few stalks to dry at home.