Catch an Eevee
Make Eevee your buddy
Walk 10 km with Eevee as your buddy
Earn 2 Eevee Candy while Eevee is still your buddy
Evolve Eevee during the day in-game
Make sure Eevee is still your buddy when you evolve it
Use the name trick once by renaming Eevee to Sakura before evolving it
If the name trick has already been used, use the buddy method instead