`not a git repository` when following install instructions for picom (a compton fork)

I'm trying to install Picom compositor on Ubuntu and have installed all the dependencies but when I get to the "To Build" section of the guide of GitHub I have to run three commands: $ git submodule update --init --recursive $ meson --buildtype=release . build $ ninja -C build None of which seem to work. Running the first returns... fatal: not a git repository (or any of the parent directories): .git So I tried making my own picom folder, running git init. This gets me to command number two which fails, responding with: ERROR: Neither directory contains a build file meson.build. I feel like I'm giving the order to build with bricks that I have yet to download. I would appreciate if someone could point to where I have gone wrong or how I might better troubleshoot my problem.