MISSED RCM TAX PAYMENT(UPTO 13/10/2017) WITH IN MARCH 2018

For example :

  " A "(Partnership firm- have GST registration and filing monthly GSTR3B AND GSTR1)

Missed to remit the RCM tax of Aug and sept 2017. Now march 2018 gstr3b and gstr1 filed.

Now(june 2018),

1.how we can remit the RCM upto 13/10/2017 ?

2. where to show in GSTR3B AND GSTR1 in june 2018?

3.HOW TO PASS JOURNAL ENTRY ,NOW, Because its a 2017-18 financial year's transaction?

Kindly give a detailed answer to overcome this problem  ...and thanks in advance