Wiring up the 2 DRV8871s is farly straightforward:

First assemble the DRV8871 breakouts as instructed in this tutorial:

From the Arduino to the DRV8871 Breakouts (we'll call them "A" and "B"), make the following connections:

• GND -> (both breakouts)
• Pin 2 -> IN1 (breakout A)
• Pin 3 -> IN2 (breakout A)
• Pin 4 -> IN1 (breakout B)
• Pin 5 -> IN2 (breakout B)

On the motor side:

• Connect one pair of motor leads to the MOTOR terminal block on breakout A.
• Connect the other pair of motor leads to the MOTOR terminal block on breakout B.
• Connect the power supply ground to the "-" terminal of the POWER terminal block on both breakouts.
• Connect the power supply positive wire to the "+" terminal of the POWER terminal block on both breakouts.