A cpu cooler will only help with cooling you cpu. It'll help with keeping the temperature in a safe range while you are using apps or games which requires a lot of cpu power. the reason why the cpu is at 100% is probably because the game is very cpu intensive - meaning it uses a lot of cpu processing power to render the game. Some games are cpu intensive and some of gpu intensive. it's not a bad thing if it's at 100%. however this could indicate a bottleneck in the system. There's tons of good videos on youtube on bottleneck.