Go to the Nerd Fonts Website

Download a font you think looks good

Create a new directory for your font to live in (system wide)

sudo mkdir /usr/share/fonts/nerd-fonts/
sudo mkdir /usr/share/fonts/nerd-fonts/FONT-NAME/

Unzip the font into the new directory

sudo unzip ZIP-CONTAINING-FONT.zip -d /usr/share/fonts/nerd-fonts/FONT-NAME/

Re-cache fonts

fc-cache -fv

Now you have your Nerd Font installed systemwide!