creating & printing postcards

I'm just trying to create a simple postcards with photos inserted in them. i created something within iphoto but it will not allow me to print it out in the format my postcard paper is printed in. It will only allow me to print a single postcard per page, and even then it is centered on the page.
Getting frustrated, seems like this should be really simple to do, but clearly I'm not getting it. Any help would be greatly appreciated. I have search the web and all I find is info about making postcards to email people or buying special software to do this.