For now, you can read the guide by FarmVilleFeed.com here
With only this much info, I suggest you Choose one now based on which bushels you still need to make the most of for crop mastery, or by which building would look best on your farm! Once you choose it, place the gnome from your gift box on your farm and you'll get a popup to share some with your friends!
Thank you Christine for this image!
If you accept:
Here's the one I chose.
Thank you Jenny for this image!
If you click to X out of it:
Here are the new gnomes on Jenny's farm.
So choose one now based on which bushels you still need to make the most of for mastery, or which building would look best on your farm!
For more information about the different stages and items needed for each type of crafting cottage check out this post by FarmVilleFeed.com.