Excellent PDF to start with a STM Nucleo and a few components (Led, push button ...) http://www.tamberg.org/fhnw/2015/LoRaWANIoTPrototyping.pdf Very basic, but very helpful.
The debug consoleOn Linux just use Minicom. You only have to specify 9600 baud. Other default values should be OK.
Type this in a terminal: 'minicom -b 9600 -D /dev/ttyACM0'.
And you should see the 'printf("Bonjour !\r\n");' in your C program.
The pins, where to plug stuff
Of course it depends on your Nucleo board, but for the L053R8, look at the Nucleo PinOut section. You have the Arduino and the Morpho headers, then focus on the PinNames.h file.
Also keep in mind the warning about D0 and D1 that are not usable, because shared for the USB communication.
Problem is that ST web site is a bit cluttered with tons of informations and it is not easy to find the relevant ones to start.
I am still reading the ST various documentation, but I did not yet find anything as useful and simple as the slides (see above)