Add Cases To Select Statment

I need to add some cases to the select statment for cpeorderstatus:

Here is my Select statement:

"SELECT O.ORDERID, C.FIRSTNAME, C.LASTNAME, O.CLIENTORDERID AS CRMORDERID, TO_CHAR(O.ORDERDATE, 'YYYYMMDD')
                  AS CPEORDERDATE, TO_CHAR(O.SHIPDATE, 'YYYYMMDD') AS SHIPDATE, O.TRACKINGNBR AS TRACKINGNUMBER, O.SHIPNAME AS CARRIER,
                  OI.ITEM AS CPEORDERTYPE, OI.QTY,
      O.STATUS AS CPEORDERSTATUS, OSN.ORD_SERIAL_NO AS SERIALNUMBER, C.BTN AS BTN, C.FIRSTNAME AS FIRST, C.LASTNAME AS LAST,
      C.SHIPADDR1 AS ADDRESSLINE1, C.SHIPADDR2 AS ADDRESSLINE2, C.CITY AS CITY, C.STATE AS STATE, C.ZIP AS ZIP, TO_CHAR(R.ISSUEDATE,
      'YYYYMMDD') AS ISSUEDATE, R.RMA_ID AS RMANUMBER, R.RMA_REASON AS REASON, TO_CHAR(R.RETURNDATE, 'YYYYMMDD') AS RETURNDATE
     FROM  SELF.ORDERS O, SELF.CUSTOMER C, SELF.ORDERITEM OI, SELF.ORD_SERIAL_NUMBER OSN, SELF.RMA R
     WHERE O.CUSTID = C.CUSTID AND O.ORDERID = OI.ORDERID AND O.ORDERID = OSN.ORDER_ID (+) AND O.ORDERID = R.ORDER_ID (+) AND
      (C.CUSTID IN (SELECT C.CUSTID FROM SELF.CUSTOMER C WHERE C.BTN='{0}')) ORDER BY O.ORDERDATE DESC"

I need to add multiple cases to cpeorderstatus, five different cases. Cane anyonye HELP