Your first blinky project works, but you don’t know how? I will explain GPIO (General Purpose Input/Output) CMSIS Library. This library is used to work with physical pins on microcontroller. You can set pins to input or output, put them low (0 volts) or HIGH (3,3 volts), select pull resistors, choose output type and select clock speed.
Ok, you got your STM32F429 DIscovery board and you don’t know how to use it. In this tutorial I will explain how to use this board with CooCox IDE. I prefer install from their CoCenter. You will need to download ARM GCC from here. There is also youtube tutorial, make sure you did all correct.