The easiest way to install Fil-C is using a binary release. It's also possible to build from source.
Fil-C currently only supports Linux/X86_64.
You can download binary releases from the Fil-C GitHub.
Once you download a release and unpack it, simply run:
./setup.sh
from the directory that you unpacked it to (for example /home/pizlo/filc-0.670-linux-x86_64). At that point, you can run the compiler using build/bin/clang or build/bin/clang++ (or via absolute path, for example /home/pizlo/filc-0.670-linux-x86_64/build/bin/clang).
Note that the Fil-C libraries are in the pizfix/lib directory, and the headers are in pizfix/include.
The compiler automatically knows how to find those headers and libraries, and will link programs in such a way that they will look for their dependent shared libraries there.
Clone Fil-C from GitHub:
git clone https://github.com/pizlonator/fil-c.git
You can build just the base Fil-C (what comes in the binary release) by doing:
./build_all_fast.sh
In the fil-c directory. If you want to also build the Fil-C corpus, which includes a bunch of programs ported to Fil-C (like Python, zsh, and others)), then do:
./build_all.sh