After the game, they’ll likely be long queues going into Norwood Junction, they close the main entrance and open the side.
But “Top tip”, as you approach the station, use the underpass/tunnel, which takes you under the station to the other side, at the end turn left then you’ll go straight in without the huge queues.
But if you do use the side entrance, you won’t go through barriers, but remember to touch the contactless reader, which are either side of the door entrance on the station. Otherwise you’ll be charged the full fare.