Homework?
Think of the things you might want to record in addition to the payment.
Probably the date on which it was made, and maybe a description of what the
payment was for (groceries, or electricity etc), and possibly also the type
of payment (by cheque, credit card, cash etc). You might think of other
things that are worth recording.
Once you have decided these things, you can allocate a column for each, and
at the end you will need a column for the payment and a column for the
remaining balance, so that you enter new data going down the sheet.
You can put labels at the top of the columns so that you know what each
column is for, and you will need a blank row in which you can put the
opening balance. As you make a payment you need to subtract this from the
balance on the previous row to give you the current balance.
Hope this helps.
Pete