From the Start menu:
Start > Programs > Rational Software > Rational ClearCase > Online Help
Start > Programs > IBM Rational > IBM Rational ClearCase LT > > Online Help
From the Help menu in any Rational® ClearCase® tool window:
Help > Help Topics. Then click Viewing IBM Rational ClearCase Manuals Online.
Help > Help Topics. Then click Viewing IBM Rational ClearCase LT Manuals Online.