1. Click the “Green flag” to start the game. Press h for help. 2. You (the human player) begin with the "Orange" coin and the computer plays with "Blue" coins. The variable “Turn” shows whose turn it is. 3. Set the slider variable "Monkey coins" to determine how many coins the computer will get to drop at every turn. 4. Click the base of the tube in which you want to drop your coin.
If you would like to understand how I designed this program, see the following article: http://www.abhayjoshi.net/spark/scratch/blog/connect4.pdf