First connect the small connector, then the bigger one. Push the cables all the way in the connectors and close them. Make sure you push the cables in far enough. Close the small connector by pushing the white part of the connector down towards the cable and close the big connector by pushing the black part down away from the cable

Once the screen is reconnected you can reconnect the battery by pushing the connector back in from the top down (see third picture).

Fix the screen on the board by screwing the screws back in place