I would plant them as soon as I got them. I think I planted mine in the spring but they didn't grow until the following winter. I had forgotten about them, thinking they were a loss so accidently dug a couple up. They were just sitting down there chilling - not grow roots or anything. They started coming up last fall and now the plants are quite large. The flowers came up first and were followed by leaves.
I bought some from Breck's and Edelweiss. Breck's sent bulbs and Edelweiss sent potted plants. The bulbs were easier to deal with but Edelweiss has a bigger selection.
Daisy