Catch an Eevee
Set Eevee as your Buddy
Walk 10 km with Eevee as your Buddy
Earn 2 Eevee Candy while Eevee is your Buddy
Evolve Eevee during the day to get Espeon
Make sure the Eevee is still your Buddy when you evolve it
Use the name trick once by renaming Eevee to Sakura before evolving, if you have not used it already