From what I see, the chocolate river has solidified, and is no longer "running". To do this you need warm but not hot melted chocolate or Merkins chocolate nibs. Then on a fondant covered cake that is room temp (not cold from the fridge) you need to pour the chocolate down the front of the cake - making sure that you catch any runoff in a dish. Neaten up the end of the river and pop it into the refrigerator to harden. It's quite simple, all the best.