If I did not put my second stimulus amount I received in January on my tax form when I filed and already submitted it what should I do?

If you have already submitted your return, you have to wait and see if the IRS adjusts your return.   You may need to file an amended tax return later.   Amending is necessary when you claimed credits (recovery rebate) that you are not eligible for.  The IRS is not accepting tax returns until Feb 12th.  If you have already submitted your return, you will notice that you can't make changes because your return is 'pending'. 

If you receive a stimulus payment while your return is being processed, wait until your return gets rejected or accepted.  If it gets rejected, you can make the change on your return before you re-submit the return.  If it gets accepted, wait until your return is fully processed and you have received your refund.   If the IRS adjusts your return, you don't have to do anything.   But if they don't adjust it and you got the payment and claimed the rebate, it is only then that you would need to file an amended return.   So, you are not going to know if you need to do the amendment until around the end of February.