I recommend you to read the STM32F0 Discovery kit's documentation as it holds many answers for many uprising questions. More documentation can be found here.
But to help you out with this one, this is the schematic of the STM32F0 Discovery regarding the boot configuration:
R27 is Not Fitted but SB2 solder bridge is on by default so the boot pin is pulled down to ground through 510 \$ \Omega \$ (R26).
Bold is the default configuration. You can change it by soldering R27 and cutting off (remove the solder) the SB2 solder bridge. All of these designators can be found on your board as white texts.