Collect the seed before the pod opens up. Now (Mid-September) is an ideal time. It’s easier to separate seeds from fluff now, and you won’t have the fluff drifting all about the room.
Open the pod along the lengthwise “seam.” Strip off the seeds with your thumb. Good seeds are brown and have some thickness in the middle–not paper thin.
Dry the seeds for a week on a counter top or in an open plastic bag.
Put the plastic bag in the basement for the winter.
On about the first of March, place the seeds in moist (not dripping) potting soil. Important: Put the pots in the fridge for two weeks. Cover the pots with plastic so the soil will stay moist.
After two weeks, take off the plastic and put the pots in a warm, sunny window. Keep the medium moist.