How did you get this .sav file? If you just copied it off your SD card, then it is encrypted and completely useless unless you have the encryption key from your 3DS.
You don't necessarily need to install CFW on your 3DS to get your encryption key - but it is the most straightforward way. If you have CFW, you can also use
threeSD to quickly import the contents of your SD card to Citra.
If you dumped your .sav from a cartridge using Godmode9, then you shouldn't have done that. Cartridge save data should only be dumped using Checkpoint or JKSM, which are homebrew utilities that run on the 3DS. (It is theoretically possible to extract data from a Godmode9 .sav dump, but it's not easy.)
If you have a .sav dumped using a Powersaves or similar device, then there's really not much you can do.
ETA: Weren't you already asking about this in
your other thread? Please don't start multiple threads about the same problem.