PWM Spindle speed control

I am trying to control the spindle speed from the software I am using a 300w spindle that uses 36v power supply.

So I am planning to us the PWM spindle pin to have 0-5v to control the power supply's voltage hence controlling the spindle speed 
The question is how do I implement and Are there any additional hardware required. 
Any help is appreciated.
 

If you are referring to those spindles with SMPS power supplies and a potentiometer for speed control, then yes, you do need other hardware to isolate that power supply from the controller.
Some controllers and some BOB's do come with the hardware required, so nothing more is needed.
More info on what controller you are planing to use.

I've got one of these
www.vallder.com/en/c/cnc-pc-cards/mach3-5-axis-board-detail

Looks good "Output 0-10V analog voltage for inverter to control the spindle speed."

It looks like it expects a PWM signal on DB25 pin 1. Stepconf should be able to configure that for you.

Also note that the BoB needs a 12V supply to the analogue output stage to become the output voltage.