Print on 4x6 paper? MF743CDW

I cannot seem to figure out how to print a message on 4x6 paper with this machine. I have set the word page setup setting to 4x6 and i cannot get it to come out as a 4x6 size, it keeps printing on what would be standard letter size. It will feed 4x6 paper thru but it will not print on the cards correctly, text always runs off the side of the sheet.