Wild Plum stones

If they are anything like the cherry i have in the garden................all you need to do is plant them ...the cherries plant themselves where they fall, and grow all over the garden.
I have to keep the hoe moving, as they are little beggars to get out if i miss them for a couple of weeks
So definitely outside, and personally i wouldn't have dried them, because naturally they stay damp, and therefore split open easily on germination.

Let us know how you get on