Missing LaTeX fonts can be added via TeXLive or MikTeX. Using the symbolic fonts is as easy as:

\documentclass[a4paper,12pt]{article}

\usepackage{fontawesome5}

\begin{document}
  \faGithub This is a GitHub logo.
\end{document}

This may need to use XeLaTeX. We use fontawesome5 instead of obsolete fontawesome, which is version 4. FontAwesome5 is in TeXLive 2018.

TeXLive is popular across operating systems. Linux users can use system package managers to install groups of TeXLive packages. Advanced Linux TeXLive users can independently setup TeXLive to get the latest packages individually, to save hundreds of megabytes of install space.

For marvosym:

Windows/Linux tlmgr:

tlmgr install marvosym

Linux: apt:

apt install texlive-fonts-recommended

For fontawesome5:

FontAwesome gives popular emoji and website icons.

Windows/Linux: tlmgr:

tlmgr install fontawesome5

Linux: apt:

apt install texlive-fonts-extra

MikTeX is another LaTeX distro on Windows. MiKTeX will automatically install packages as needed. If that isn’t happening, check:

Start → MiKTeX Console → Settings → General → “Always install missing packages on the fly”

Otherwise, manually search for package name and install:

Start → MiKTeX Console → Packages