Modify the partition

I created one table with a RANGE PARTITION.
CREATE TABLE SAMPLE_ORDERS
(ORDER_NUMBER NUMBER,
ORDER_DATE DATE,
SHIPPING_DATE DATE,
CUST_NUM NUMBER,
TOTAL_PRICE NUMBER,
TOTAL_TAX NUMBER,
TOTAL_SHIPPING NUMBER)
PARTITION BY RANGE(ORDER_DATE)
(
PARTITION SO99Q1 VALUES LESS THAN TO_DATE(01-APR-2005, DD-MON-YYYY),
PARTITION SO99Q2 VALUES LESS THAN TO_DATE(01-JUL-2005, DD-MON-YYYY),
PARTITION SO99Q3 VALUES LESS THAN TO_DATE(01-OCT-2005, DD-MON-YYYY),
PARTITION SO99Q4 VALUES LESS THAN TO_DATE(01-JAN-2006, DD-MON-YYYY),
PARTITION SO00Q1 VALUES LESS THAN TO_DATE(01-APR-2006, DD-MON-YYYY),
PARTITION SO00Q2 VALUES LESS THAN TO_DATE(01-JUL-2006, DD-MON-YYYY),
PARTITION SO00Q3 VALUES LESS THAN TO_DATE(01-OCT-2006, DD-MON-YYYY),
PARTITION SO00Q4 VALUES LESS THAN TO_DATE(01-JAN-2007, DD-MON-YYYY)
)
;

I want to modify the partition based on SHIPPING_DATE. Whats the steps for implement it?
Thanks!