To print this flexagon print 3 of the “Flexagon Regular” files along with 3 "Filament Hinge Link' files. You can also print the looser tolerance file if your printer is not very accurate. Print the Snap On Link at your own risk as I have had limited success with a snap on link. 

To assemble the flexagon, cut 6 bits of filament about 12mm long, put the hinge between the 2 prongs then push the filament into the hinge and the prongs. Repeat for all the sides until fully assembled. I posted some pictures to help visualise the assembly.