From file manager I open 'public-html'.
I click 'install'.
I open 'index.php'
shows file Url: http://mydomainname/install/index.php
I open it & it shows : Webcalendar database setup
' your current database settings are able to access the database'
I click database test settings, and it shows 'SUCCESS'
I click 'save settings', and all is OK
I click 'Launch Webcalendar', and it shows 'WEBCALENDAR ERROR' - 'ILLEGAL CHARACTERS IN LOGIN.'

Did you remember to delete the install file? You really should let Fantastico install this stuff for you.