1. Download and extract.

       2. Locate `refind` directory under EFI partition. For most Linux based system is commonly `/boot/efi/EFI/refind/`.
           Copy theme directory to it.

           Important: Delete older installed versions of this theme before you proceed any further.

       sudo rm -rf /boot/efi/EFI/refind/{regular-theme,refind-theme-regular}
       sudo cp -r refind-theme-regular /boot/efi/EFI/refind/
        
    3. To adjust icon size and font size edit theme.conf
.
       sudo nano /boot/efi/EFI/refind/refind-theme-regular/theme.conf

    4. To enable the theme add include refind-theme-regular/theme.conf at the end of refind.conf.

       sudo nano /boot/efi/EFI/refind/refind.conf