Money Order is a 'pre-paid' check issued by your bank or any financial institution where the money is taken away from your bank as soon the they issue the check. This way the one who receives the checks is guaranteed payment right away without having to wait for the check to be cleared.
So what you need to do is go to your bank (or any bank but you have to pay them the check amount upfront) with the name of the beneficiary, and the amount you need to pay, and they will issue a money order which you can send to the seller. The issuing bank may charge you a small fee for this service.
Foe more information about money order see this article:
Hope this helps.