Get the Popcorn Achievement in Halo Infinite
View a clip in theater.
A quick way to get this one is to start a custom game from the main menu and ending it straight away. At the main menu screen press RB to go along to Community. Select the first option for Theater and then the second option down for My Match History.
The match you just played should be there, so press A to watch it and the achievement should unlock as soon as it’s loaded.