1) After reviewing the grammar point, give a sheet to each student. Review all objects.
2) Have students cut out the battleships into five pieces. You may need to bring a few extra pairs of scissors in case students don't have any. Demonstrate yourself that they can be cut in twenty seconds or students may take too much trying to do a perfect cut.
3) Demonstrate with two desks and the JTE how to play the game. You might want to make a big version and put it on the blackboard.
4) If you don't know, Battleship is this: Each player has ships, for this game they have two. They can place them anywhere they like on the board. Have the students use textbook/pencil case/notebook combinations to block their opponents from seeing their boards. Students take turns asking each other questions. Have them play RPS (rock, paper, scissors) to decide who asks first. The student who wins then asks, "Can I use your (camera)? If the opposing player has a piece of one of their battleships on "Camera", then it is a "hit" and the answer is positive (sure, go ahead, OK, etc). The player who made the hit can take their pencil and mark on the sheet to guess where the rest of their opponent's battleship might lie. If there is no ship on "Camera", the answer is negative (Sorry, you can't, etc). If a piece is hit, the player then removes that piece. If an entire ship is sunk, the student can say "You sunk my battleship!" (or something easier...). If both ships are sunk, the player with ships or ship pieces remaining is the winner.
Don't spend too much time explaining. Make sure you practice with the JTE before class so that they can explain if the kids don't get it. Use demonstrations and torpedo/explosion gestures. The kids can pick it up pretty fast on their own once they get the gist of it.