JDFTx is distributed as source packages, or for development via git, and requires a POSIX-compatible environment and a C++11 compiler to install and get running. It also depends on several GNU and open-source libraries, which will most easily be installed using a package manager. So here are the prerequisites to installing JDFTx on your system:
GNU/Linux (any distribution): You already have a package manager (or you are on an advanced distribution and know how to do without one!). In high likelihood, your distribution is either:
See Linux Package Management for a detailed introduction.
Windows: On Windows 10, use the Windows Subsystem for Linux to get a minimal Linux environment and then follow the Linux installation procedure within it. This option is easier on Windows and yields better performance, but does not support the graphical tools.
The other alternative is to install Cygwin, which provides a POSIX-compatible environment on Windows including a terminal with the bash shell (assumed here and in the tutorials). You can select packages in the Cygwin installer graphical interface, and can rerun the installer to add / remove packages later. In addition, you should select the xinit package to get a working X11 environment, which will be necessary for operating many of the Unix tools in graphical mode.