You can let the seed pods mature and when they start to turn brown and split on the sides, collect the seeds before they drop to the ground.
There are a variety of different ways to deal with the seeds, but you need to dry them out then subject them to cold. Some people put them in the refrigerator soaking, some put them in the freezer. I think the refrigerator works best for me, but I am not an expert on this.
If you plant them in a pot and leave outdoors during the winter, some should sprout in the spring. Some will not sprout until the following year!
If you are patient you will grow an iris that is brand new! No one has one exactly like it, and it will be your own creation. What will it look like? There are so many variations on color that it could be any of many possibilities.
Good luck,
Laetitia