Unable to install Customizer using PPA and LXTerminal

I am trying to add Grub Customizer to Lubuntu 15. The terminal seems to keep leading me in circles:

john@john-GA-890GPA-UD3H:~$ XXXXXXXX
OLDdoc77018: command not found
john@john-GA-890GPA-UD3H:~$ sudo add-apt-repository ppa:danielrichter2007/grub-customizer
[sudo] password for john:
Sorry, try again.
[sudo] password for john:
Sorry, try again.
[sudo] password for john:
Sorry, try again.
sudo: 3 incorrect password attempts
john@john-GA-890GPA-UD3H:~$ XXXXXXXX
OLDdoc77018: command not found
john@john-GA-890GPA-UD3H:~$ sudo add-apt-repository ppa:danielrichter2007/grub-customizer
[sudo] password for john:

When I try to type in my password, nothing happens: I copy and paste the first line of the PPA. Terminal asks for a password.
But I am unable to type the password in the space alloted- it is blocked. Is this a Terminal problem? I Customizer not compatible with Lubuntu?

John