graphic card

hello, I have recently bought a dell inspiron 5567 core i 7 - 7th gen which has dedicated memory 128 MB :emotion-43: and also it has radeon graphics  installed, but i don't know how to switch between them,  I opened radeon ,in the gaming part it had option named add. I installed a game and added it to the gaming part in radeon graphics , but it didn't work. every time I open the game an error " the video card does not meet necessary specifications (GPU= VRAM 512Mb)" occurs. so what should I do ? is there anything I should install?