Find the location on the amplifier bank that has the A Axis / 4th Axis label. Install the amplifier for the fourth-axis drive at this location.
Connect the fourth-axis servo cable wires to the high-voltage terminals on the amplifier:
- red to RED 
- white to WHT 
- black to BLK 
Connect jumpers  from the fourth-axis drive to the nearest amplifier on each side:
- Connect the black wire to -H.V..
- Connect the red wire to +H.V..
Caution: On older machines the fourth-axis servo cable may have a shielded wire attached to the black jumper. Connect the shielded wire to -H.V. Do not connect it to the machine ground.
Put the cables in the cable tray.