To see if an app is using the higher-performance discrete GPU, open Activity Monitor and click the Energy tab. Just to be clear, you wouldt WANT your card to idle at 51c, lower is always better, but thats just to give some perspective.
For some reason though, it seems that Skyrim cannot detect the Radeon. My laptop has two graphics cards, one Intel and one Radeon, and it is supposed to switch between them when required. Технические характеристики видеокарты ATI Radeon HD 6520G: I have been playing Skyrim for about a week and today I realized that Skyrim uses the Intel (R) HD Graphics 520 adapter instead of the AMD Radeon (TM) R5 M335.