Instructions
Collect seeds. You can do this in several ways, but the easiest is to tap on the flower next to Tinkerbell's house on your touchscreen. Seeds will shake loose, and you can collect them.
Find Olwen. You can find her in Spring Valley, the Midsummer Hills or the Summer Glade.
Interact with Olwen by tapping on the touch screen. Give her your collected seeds, and she will give you the flowers that grow from them in return.