Important: You must install NerdFont (and configure your Terminal to use it) first.

To update (replacing the current version) run webi vim-devicons.

These are the files / directories that are created and/or modified with this install:

~/.vim/plugins/devicons.vim
~/.vim/pack/plugins/start/devicons.vim/
~/.vimrc

Adds icons to NERDTree, vim-airline, CtrlP, unite, Denite, lightline, vim-startify and many more

vim-devicons is fairly plug-n-play. Install it, and it works.