use the curl command or for use in scripts.
Linux
mkdir -p ~/.local/share/fonts
cd ~/.local/share/fonts
curl -fLo "Droid Sans Mono for Powerline Nerd Font Complete.otf" https://github.com/ryanoasis/nerd-fonts/raw/master/patched-fonts/DroidSansMono/complete/Droid%20Sans%20Mono%20Nerd%20Font%20Complete.otf
macOS (OS X)
cd ~/Library/Fonts
curl -fLo "Droid Sans Mono for Powerline Nerd Font Complete.otf" https://github.com/ryanoasis/nerd-fonts/raw/master/patched-fonts/DroidSansMono/complete/Droid%20Sans%20Mono%20Nerd%20Font%20Complete.otf