Now I am trying to alter the index and I am getting another error.

alter index value_date_idx
add partition x_icm_jan2002 values less than
( to_date('2002-02-01 00:00:00','SYYYY-MM-DD HH24:MI:SS','NLS_CALENDAR=GREGORIAN'))
tablespace index_hsbc_icm_jan2002;

add partition x_icm_jan2002 values less than
*
ERROR at line 2:
ORA-02243: invalid ALTER INDEX or ALTER SNAPSHOT option