At the moment, Sitix has no prebuilt binaries; I hope to include RPM/DEB packages in the next release.
To install it, you'll need to clone the Github repository, run ./build.sh, and (assuming the build completes successfully) copy the generated sitix binary to some PATH-accessible location (/usr/bin is a good bet). Sitix requires a C++20-compatible G++ installation; it has no other dependencies. Sitix is theoretically cross-compilable to Windows, but I have no intention of ever officially supporting Windows.

Once you've got Sitix installed, see Usage.