How can I add ROW_NUMBER() into my query that has joins?

Hi,
I am looking to paginate the results of the query, so I need to use
ROW_NUMBER() OVER (ORDER BY ...) AS Row_Counter
and then put:
WHERE   RowNum >= 1
    AND RowNum < 20

but I am not sure how to add it into this query that already has two joins.
Here is my current query:

$data_query = mysqli_query($conn, "
SELECT ZIPCodes.zipcode, usersearch_answers.username,
       (3959 * acos(cos(radians(ZIPCodes.latitude)) *
       cos(radians(center.latitude)) *
       cos(radians(ZIPCodes.longitude ) -
       radians(center.longitude)) +
       sin(radians(ZIPCodes.latitude)) *
       sin(radians(center.latitude)))) AS distance
FROM
(
    (
        SELECT usersearch_answers.username,
            usersearch_answers.zipcode,
            ZIPCodes.latitude,
            ZIPCodes.longitude
        FROM
        (
            usersearch_answers JOIN ZIPCodes ON usersearch_answers.zipcode = ZIPCodes.zipcode
        )    
        WHERE (ZIPCodes.zipcode='33133')
    ) center, ZIPCodes
) INNER JOIN usersearch_answers ON ZIPCodes.zipcode = usersearch_answers.zipcode
WHERE (usersearch_answers.username <> '$userLoggedIn')
HAVING (distance < 5000)
ORDER BY distance");

How do you combine the two?
Any tips are so greatly appreciated!  
-Aimee