An official English dub or sub has not yet been announced for Boruto: Naruto the Movie or The Day Naruto Became Hokage anime special.
That new anime special is based on The Day Naruto Became Hokage manga and will show Naruto’s Hokage inauguration and the events that lead up to it.
We’ve seen that too through The Day Naruto Became Hokage one-shot manga chapter by Naruto creator, Masashi Kishimoto.
We’ve seen a bit of his life after becoming Hokage through the Naruto Gaiden: The Seventh Hokage and the Scarlet Spring manga and Boruto: Naruto the Movie.