each motherboards bios is different, but if you go into the motherboards bios and look in advance. you would normally find an "IGPU"(or onboard graphics) setting. it might say "auto" you would need to click it to manual, and more options will appear underneath . and it will give you option to increase the onboard graphics size from 64mb all the way upto 32gb.. but the rule of thumb is " half and half max". so if you have 8gb ddr ram(you can only have upto 4gb onboard graphics, 16gb ddr(8gb onboard),32gb ddr4(16gb onboard graphics),,etc.. as for ocer clocking , again you would have to search for it.(it might be in the same place as where you up the onboard graphics).. you can increase its speed from +50-200 mhz.. but make sure you have good cooling. on CPU. so you dont overheat. im currently running my ryzen 3 3200g (im using a nvidia 1050ti now, but for 3 weeks i was on my onboard IGPU, using 4gb ram(i could have upped it to 8gb) and over clocked it by 150mhz. and it was fine. played the games no issues.
my ryzen 5 5600g arrives in a few days. for some readon amd chose to lower the onboard IGPU to vega 8, when other older cpu's had vega 11 , but the core speed for the IGPU will be 2000mhz,(or 1900mhz).