1) Download Luma3DS 5.5 ZIP
2) Extract arm9loaderhax.bin in somewhere at your PC
3) Drag and drop THAT arm9loaderhax.bin in pathchanger.exe
4) Type, for example: luma/luma3ds.bin and press enter. The program will now close, but it actually altered the arm9loaderhax.bin file.
5) Rename THAT arm9loaderhax.bin file to luma3ds.bin
6) Create a folder in your 3ds microsd card named luma
7) Put luma3ds.bin in that folder (luma, which you just created)
8) Configure your boot manager (create a new entry that points to luma/luma3ds.bin)
9) DONE