This bootloader uses the same configuration as bootctr. 
If you use delebiles arm9loaderhax you can put the arm9loaderhax.bin and the arm9bootloader.bin file on the root of your the 
sd-card, if you use my forks arm9loaderhax you only need to use the arm9bootloader.bin.
This bootloader defines which payload should be bootet by the key you press while powering on your 3DS.
