How to add to Where clause depending on parameter value

I have an sql query that I am wanting to run and want to add something to the where clause if I mark a parameter as true. I didn't think I would need to have the same sql statement twice, but can't find a way to do this. This is what I want.

DECLARE @getShipped VARCHAR = 'false'; 

SELECT DISTINCT 
    Serial_No
INTO #Serials
FROM Part_v_Container_Change2 AS CC
WHERE Change_Date <= @dateEnding
   *** AND IF @getShipped = 'true' THEN CC.Container_Status = 'Shipped' ***

Have tried if statements and case statements but can't seem to get this to work? I just don't want to repeat sql if I don't have too.