At the bottom of the motor controller there are 3 Terminal Blocks.
These are labeled:
Motor 1 & Motor 2 - These are the motor blocks. In each block you can wire one motor into each block. These are Bi-directional so it doesn't matter which side of the motor goes into the pins on the block. The direction is then controlled via code.
VCC2 - This is the power in to power the motor controller IC and is the power source for the motors. PLEASE NOTE THE WIRING. The voltage in is polarised and wiring this wrong CAN DAMAGE the mcb, Batteries, and even your Raspberry Pi. Just make sure when wiring that the positive power wire (usually red) goes into the left side of the terminal block and the negative (usually black) goes into the right side of the terminal block.
Motor Controller V3 GPIO Wiring
The new MCB breaks out the GPIO pins to the side of the board instead of using an extended header. We found in testing this works better and is more robust than the extended header.