user priviliges

Hi DBA's,
I am trying to investigate the following error:
ORA-02063 user USER1 lacks CREATE SESSION privilege; logon denied
I know before the user can create a session and do anything he/sqe has to have a 'create session' privilige. Please let me know what I need to do.
Thank you.

log on as SYSTEM and 'grant create session to user1;'.

thanks