Supposing that the smdhax installer works in sky3ds' roms, you would need 2 3ds, yours (vanilla, with nothing) and a hacked 3ds (with homebrew and the smdhax installer at least)
- put a smd rom on your sky3ds and insert it on the hacked 3ds
- go to homebrew menu and run the smd installer
- it will ask for the model and version of your 3ds (you have to put it acording to the model/region/fw of your 3ds, the vanilla one)
- once done, you can use your sky3ds as an entrypoint on your vanilla 3ds (now you'll need to download the starter kit an paste it in the 3ds' sd)