Get the current devkitPro http://sourceforge.net/projects/devkitpro/files/Automated%20Installer/devkitProUpdater-1.6.0.exe/download ; install toolchain for ARM, it will automatically fetch dependencies (ca. 40MB).
Leave the C:\devkitPro
default directory as is.
Get Makerom https://github.com/profi200/Project_CTR/releases/download/0.15/makerom_015_ctrtool.zip and extract the two .exe files into C:\devkitPro\msys\bin
Get precompiled portlibs https://github.com/xerpi/3ds_portlibs/releases/download/1/portlibs-windows.zip and extract the portlibs folder into C:\devkitPro
Install Git for Windows.
Open an Msys prompt from the devkitpro start menu entry.
"C:\Program Files\Git\bin\git.exe" clone https://github.com/smealum/ctrulib.git
"C:\Program Files\Git\bin\git.exe" clone https://github.com/xerpi/sf2dlib.git
pushd sf2dlib; "C:\Program Files\Git\bin\git.exe" checkout effe77e; popd
"C:\Program Files\Git\bin\git.exe" clone https://github.com/xerpi/sftdlib.git
"C:\Program Files\Git\bin\git.exe" clone https://github.com/J-D-K/JKSM.git
In explorer, open C:\devkitPro\msys\home\yourusername
, copy all folders into C:\devkitPro
[1] latest sf2dlib => blank screen when launching homebrew, see J-D-K/JKSM#4
Compile and install libraries :
cd "C:\devkitPro\JKSM"
make cia
FS_* API from libctru - result codes breakdown in C:\devkitPro\ctrulib\libctru\include\3ds\result.h