Power - Turn on power by following the game hints.
Upgrade - You can either buy monkey bombs at a crafting table or hope some zombies drop them. Now go to any of the three aether reactors and get 50 kills with the monkeys bombs. This should around three monkey bombs. You will you have completed it when it starts glowing red and the zombies dance. This causes the bombs to do more damage and every player will now have upgraded monkey bombs.