While do you want to use such an obsolete development environment? Let me suggest you a more modern alternative to turbo C, like
Visual C++ 2010 Express[
^].
Anyway, for building a (very) simple game (let's say a 2D one) you need to learn how to draw graphics primitives on the screen (BGI with turbo C, GDI or GDI+ with Visual C++) and a bit of physics.