Zplosion :
I don't understand how to
How to do what exactly? Why on earth would you want to use igpu when the provided dedicated gpu chip is stronger in performance?? AMD designed their mobile chips to be power efficient so i don't see if you are concerned about battery usage.
If you are really that persistant into changing into igpu and going through the hassle of rebooting your laptop to go back to dedicated chip whenever you want to game there is only one method to do that.
Go into bios when your computer is booting (del or f12 or whatever key it is) and go into peripheral section. There should be an option to change display adapters and choose either igpu or dedicated chip.
Honestly there is no reason behind what you are doing.