In emacs, if you ever run into the need to have access to all the icons and fonts, may it be for doom-emacs icons bar, or centaur-emacs icons and font or Spacemacs icons,
you will have to run this command inside of Emacs (M-x meaning Alt+x which is to access the Emac's mini-buffer)

M-x all-the-icons-install-fonts

BUT THEN it is important to go to the folder where you installed the fonts and install manually all the files that appeared after this command.

Now, make sure to click and install every one of them. After which the icons should show nicely on your Emacs.

enjoy :D !