Create your password by typing
Enter your password.
This will generate a long and encrypted password.
Copy the whole generated code and Edit the file
/etc/grub.d/00_header using vi, leafpad, nano e.g
# vi /etc/grub.d/00_header
# sudo leafpad /etc/grub.d/00_header
Go to the end of the file.
Type the following command
cat << EOF
password_pbkdf2 username 'paste the generated code copied above here'
Save the changes and exit the editor & update grub using either of the commands
# grub-mkconfig -o /boot/grub/grub.cfg
To test the changes, reboot the system.
If the procedure above was successful, once you select grub entry to boot, you will be prompted to enter username and password.
Enter those credentials and your grub is secured!!!!