I was wondering because I've catch millions of pokemon but none of them can use it.
You can't us an oval stone it is a hold item.You make happiny hold the oval stone.After you make happiny hold the oval stone it will evolve into chansey.When you get chansey you can evolve it into a blissey with high friendship
The Oval Stone is used to evolve Happiny into Chansey. Happiny must hold the stone, then you level it up during the day.