This is a software controlled video system - only the Intel GPU has a physical connection to the screen, so ALL video data passes through it, even if it came through the AMD GPU. As a result, in the game and under Windows, the Intel GPU is the only one you'll ever see.
You SHOULD see a difference in gaming performance between running it with or without the AMD coprocessor, which you select using the catalyst control panel -- that is, IF the game supports hybrid video. Not all games - particularly older ones - support hybrid operation. Some may not be written for such a system, and others may require an update or a paid upgrade to run in hybrid mode. Check with the individual game publisher for recommendations on setting up hybrid video operation. Also note that there are plenty of games out there that don't run well under Windows 8, particularly 8.1 - you may need to run them in Windows 7 or earlier compatibility mode.