No console ouput
Hi Max,
Welcome to the world of embedded systems. Your discovery board does not have a console unless you build one. If you google "stm32f4-disco console" You will find information on how to do this and you will then know more about it than me.
I should look into that. In the mean time I have used buttons and such for user inputs. I'm working up to using touch on the STM429I-DISCO.
Another interesting I/O option would be a small radio like the nrf24l01 or the esp8266.
best,
hank
Edit: You might find this link interesting: http://www.wolinlabs.com/blog/stm32f4.semihosting.html