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Questions &/or issues related to products in the Robotics category should be posted in this forum. Includes Direct Current(DC) Motors & Drivers, General hardware & Chassis, Servomechanisms(Servos) & drivers, Stepper Motors & Drivers, etc.
This isn't something we support, but the pins exist on the Stepoko board.

For spindle control you need 2 pins, SPINDLE_DIR and SPINDLE_PWM. Those are on pins D13 & D11 respectively and control direction and speed.

For coolant, you want COOLANT_ENABLE and that's on pin A3.

Check the GRBL0.9 documentation for details on what G-code is needed to enable and control those pins.