See Rambling Joe's response of Nov. 1, 2012. It is very clear, and, most importantly, it works.
Add to the above
4.a. Select Contact Sheet from the list of options in left column iin new window
4.b. Select paper size (below image)
5.a. OR, select "custom" and enter the size in inches of the print you want to make
Amend step 9 to read: Click on the arrows in teh "Photos Per Page" box to choose one of the three options, the third one being "Multiple of the same photo per page." iPhoto zooms in and crops the photo to fit the space available (though this step did not happen to my job). To make a photo full-frame, Control-ckick the phot, and then choose "Fit Photo to Frame Size" from the menu that appears.