How to set NLS_CHARACTERSET = UTF8 in Oracle 11gR1?

Hi all,
I try to replicate a customer's environment for Oracle 11g on AIX.  Customer gave us the NLS settings as follow:

SQL> select * from NLS_DATABASE_PARAMETERS
PARAMETER                      VALUE                                    
------------------------------ ---------------------------------------- 
NLS_NCHAR_CHARACTERSET         UTF8                                     
NLS_LANGUAGE                   AMERICAN                                 
NLS_TERRITORY                  AMERICA                                  
NLS_CURRENCY                   $                                        
NLS_ISO_CURRENCY               AMERICA                                  
NLS_NUMERIC_CHARACTERS         .,                                       
NLS_CHARACTERSET               UTF8                                     
NLS_CALENDAR                   GREGORIAN                                
NLS_DATE_FORMAT