It depends on who your master card is with. Also, there are many ways to pay it. Your statement should have all the information on it such as;
the due date.
where to send the payment.
how much the minimum payment is, (try to pay more than the minimum if you can and it will save you money on interest payments).
You can make payments by using, checks, money order, western union, or set up automatic payments from a checking or savings account.
You should also have a phone number of the company that issued the master card and they will tell you more about your issued card.