Order PCB's and parts. elecrow/seeedstudio/dirtyPCB's can all make these boards and other manufactures should also have no issues with them. Parts can be bought from Farnell. The BoM file lists the Farnell numbers. A few parts like the numitrons can be bought on Ebay.

Solder the parts on the PCB, SMD first, trough hole next.

Program the binary file to the microcontroller. To do this, hold the boot button, then plug the USB in, then release the boot button. Now the board is in bootloader mode and the binary, the .dfu file, can be programmed using the ST tools on Windows ( http://www.st.com/en/development-tools/stsw-stm32080.html ) or the dfu-util on Linux ( http://dfu-util.sourceforge.net )

Reset the board with the reset button or by unplugging and plugging it back in again. The numitrons should turn on now, showing all zeroes.

Set the time with the 4 buttons. Each button press increases the numitron the button is behind with 1.

Enjoy your clock :)