See the README one level up about where to find the reference manual
for the stm32f4 and schematics for the board.

There are a number of leds on this board, four of them are grouped
together on Port D 12, 13, 14, and 15.

Looking at the reference manuals for the stm32 value line part and
this part they have a lot of differences, you really have to just about
start over finding what you need to do to turn on the port and blink
some leds.

If this is your first cortex-m3 I hopefully have better information in
my mbed_samples repo (also at github) look at the first few blinkers.

This example is in C with some asm to get things started.  Both gcc
and llvm's clang are used to create various flavors of binaries from
the same source.  The code is quite trivial but this hopefully creates
a foundation of how to use these tools for an environment like this.