Printer on Xubuntu: Password problem

[H.S.Rai]

I tired to install printer using http://127.0.0.1:631 , but it failed
to accept username and password. After searching Internet, I used
"lppasswd -a some_user_name, but above site did not accepted new
username and password.

I tried to use command line as below, as root user, and also tried as
cupsys user:

 lpadmin -p myPlotter -E -v parallel:/dev/lp0 -m HP-DeskJet_420C-hpijs.ppd

and this resulted in error that "unable to copy PPD file!"

I tried above command with -U userCreatedWith_lppassword

Please help me set printer on xubuntu.

-- 
H.S.Rai
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