I assume you are talking about a laptop with switchable graphics. Some manufacturers allow you to turn the IGP (integrated) graphics off in the bios. Look for graphics or display in the bios, and change from 'dynamic' or 'switchable' to 'fixed' or 'static'. This forces the laptop to use only the dedicated (AMD) graphics. Not all laptops have this function/choice.
In BIOS I can choose between dual graphics and "UMA only".
Both graphics are made by AMD. When I turn off integrated graphics by device manager it's shown that dedicated card doesn't have drivers(in catalys both cards are visible).
There is no difference visible in FPS during playing any game while dual graphics or APU is activated. Option of graphics can be chosen in catalys.