The 5W laser you have requires a separate power supply. the CNC controller card does not have sufficient power to run it with the steppers.
The three pin on the laser controller card, you should have received a pig tail, with 2 leads into a barrel pin for the external power supply. Attached to this is a small single lead with a molex plug that could be connected to the “S” pin. This would allow a PWM signal. I recommend, do not connect this connection.
On your laser control board you will see a 2 pin connector labeled +TTL and -TTL, connect as follows to your CNC controller board.
Go to your local electronics store and pick up Female to female 28 AWG jumpers, small pin.
Jumper the +TTL (laser control module) to 3 pin connector of your CNC card to the “S” pin.
jumper the -TTL (Laser control module) to 3 pin connector of your CNC card to - Pin (same connector you jumped the “S” connection).
Power up your CNC card first, then power up your Laser control Module to allow the “S” pin signal to prevent momentary laser full power on.
This should now give you a laser with TTL logic to process.