Apple ID on apple watch problem

My dad went to a store to by me an apple watch series 4 then the costumers told him that they have to set up the watch to make sure that every thing is good. All was fine. At the end thay reseted the apple watch and removed it from the watch app from the phone but now when i want to connect my phone to the watch the apple id from my dad's phone is sitll there. what can i do to remove the apple id from the watch and connects mine. Thanks!