You lucky girl! What a great gift! Try your middle finger, on either hand, I personally love wearing diamonds there~ it's so cute and fresh, especially if you're wearing diamonds with a slight bit of irreverance and going casual. Fancy stones with jeans is so modern and vibrant. I believe that it is so beautiful to interject lovely objects at every point possible and nothing is more lovely than sparkling stones. Don't forget any jewelry shop worth their salt (or stones!) should be able to resize your ring for any finger, which ever you choose.