well its up to you but you go to a store that sells money orders (usually small little stores - just ask someone they will know)
and buy the exact amount you need (you can purchase up to 500$ so if its like 650$ -you would need a 500$ one and a 150$ one)
they charge you per money order but its usually under a dollar
then you mail the money order to the company or whereever - its pretty much like a check
when they get it they ship it