SPWM by using dsPIC30F2010 Compiler is MikroC Pro for dsPIC

The questions you are are about how to set the clock speed which is fundamental to the operation of the whole MCU but is possibly the wrong place to start.
Assuming you know the basics about how the MCU works, start with the PWM signals that you want to create.
You could use the PWM signals to drive the IGBTs (etc.) in which case all you need is to set the PWM frequency to the frequency you want to general (50Hz or 60Hz) and set the duty cycle to 50%. However there are probably many easier ways of generating this signal that using a (rather old it must be said) MCU and its PWM module.
If you want to use the PWM to generate a pseudo sine wave, then you need to know the number of steps you want per cycle as well as the overall frequency (as above). Then you can set the duty cycle in increments from 50% at the start of the cycle, to 100% at the top of the first crest, back to 50% and then down to 0% for the bottom of the cycle before returning to 50% at the end. The output will then need to be filtered to remove the higher frequencies but that will give you a sine wave that you can amplify. (The schematic you have shown doesn't seem to follow this approach but you can create you own circuit.)
Once you have the PWM requirements, you can use the MCU data sheet to determine the system clock frequency you need to feed into the PWM module. The data sheet has equations 14-1 to 14-3 that will help here.
Susan

Hi

I guess there rather are too much than too few SPWM tutorials.
Many are very good, with detailed explanation, calculation examples, code, scope screenshots ...

Klaus