Hi Deborah,
The seed saving course will be released very soon but I’m happy to share some information in the meantime.
Generally, for harvesting seeds, you want to let the seeds mature on the plant. So for poppies, you need to wait until the seed heads turn brown and you can hear rattling inside the pod. Then, you can carefully clip the pod head and bring it inside or, bring a jar or bag out to the garden with you to dump the seed head into. At this stage, you can eat the poppy seeds too. Here’s a good blog post
I found about harvesting poppy seeds: https://www.gardeningknowhow.com/ornamental/flowers/poppy/saving-poppy-seeds.htm
When seeds are mature and ready to harvest, they will release from the plant easily, if not, they need more time. It is often good to lay out your seeds to dry a bit more inside before storing them.
As I said, the course is coming super soon! Will will let you know this week.