Instructions
Capture a Seadra. Although they can be found in the wild in many of the "Pokemon" games, a Seadra will evolve from a Horsea once it reaches level 32.
Find a Dragon Scale. The method of locating one differs from game to game, but in "Pokemon Black" and "Pokemon White," a Dragon Scale is lying on the ground behind a large rock on Route 18. Use a Pokemon that knows the move "Strength" to move the rock.
Give the Dragon Scale to Seadra to hold. Select Seadra in your party of Pokemon, enter the Item menu and choose the "Give" option. Scroll through your item bag and select the Dragon Scale to make Seadra hold it.
Trade Seadra to another version of "Pokemon" while it is holding the Dragon Scale and it will automatically evolve into Kingdra when it arrives. Send Kingdra back to your version of "Pokemon" so you can enjoy the benefits of the mighty Dragon on your Pokemon team.