I need help to do both -hi-lites and lo-lites on my hair. It's short it back long in front.Can someone plz hlp?

My hair is a dirty blonde and for the lo-lites im doing strawberry blonde and the hi-lites im doing a white blonde (hair dresser suggested those colors) but im not sure on wear abouts to put the colors. I know the strawberry blonde will go in back and the white blonde on top but i don't know were to start and stop them....