To connect two devices you'll need internet access, you don't need to be in the same room, even in the same country, but you will need to activate your Google Play Game account in both devices, you have instructions inside the game.

To make the prank you need two devices, one to control and one to show the pencils, then use the power of suggestion and the pencils will start moving without anyone touching them, except when you are going to need to reset the pencils, and this might seem spooky in the right setting, answer the questions right to make the mood, and then show Charlie.

This is how the real game, the Charlie Charlie Challenge works, players balance one horizontally aligned pencil on top of a vertically aligned pencil (essentially, in the shape of a cross). Both writing utensils sit atop a piece of paper divided into four quadrants. Two of the quadrants are labeled "yes" and two are labeled "no." Players then invite a spirit, Charlie, to play with them.