The easiest way to install nihstro is to find a precompiled version of the nihstro-assembler and nihstro-disassembler. You can put them in any location and add an environment variable "NIHSTRO" which points to that location.
If you need/want to build nihstro yourself, you first need to install CMake and the C++ Boost libraries. CMake has an installer for Windows, and is most likely available via your package manager on Linux.
To install the Boost libraries, download the latest package from the boost main site and extract it anywhere. Open a command prompt (windows) or terminal (linux) and navigate (
cd) to the extracted folder. Now run
boostrap.bat (windows) or
./bootstrap.sh (linux). It will generate a b2 executable. Install boost via
b2 install --prefix=c:\boost (windows) or
./b2 install --prefix=/usr/local (linux).
After all that is done, download and extract the nihstro package and
cd to it in your command prompt/terminal. Now use the commands
cmake . and
make to compile nihstro. Finally, add an environment variable called "NIHSTRO" and point it to your nihstro folder (the one containing the assembler and disassembler).