The first step was to solder the Numitron tubes to the pcbs. The PCBs are quite simple and just consist of a pair of shift registers, two tubes and a diode. I found the pcb here.

After soldering the tubes I connected the Arduino and created the mapping for each number. The mapping can be found in the linked Github repository. The idea is to map the right bitmapping to each number for one tube:

byte digit[10]= {B00100001, B11111001, B00010101, B10010001, B11001001, B10000011, B00000011, B11110001, B00000001, B11000001};