Enter the below listed commands if you haven't installed any theme before you have to generate the configuration files for bat and theme dir.
bat --generate-config-file
mkdir -p "$(bat --config-dir)/themes"
cd "$(bat --config-dir)/themes"
If you already have the configuration files just
cd ~/.config/bat/themes/
git clone https://github.com/Everblush/bat
bat cache --build