So, let’s first complete the wiring.
Each motor needs 2 signals, one for the clockwise movement, one for the counterclockwise movement.
I’m using the GPIO 18 ,23,24,25 connected directly to the 4 inputs of the bridge. See the diagram below.
Consider Motor 1. When GPIO 18 is high , the bridge set the Out1 also High and Out2 is the ground. And the motor turns cw. When GPIO23 is High the bridge inverts the outputs, so Out1 become the ground and Out2 is High and the motor turns ccw.
Finally , as we see in preview post, modulating the pulse width of the signal we can control the speed of the motors.