How do I print multiple photos on one page?

This depends on your printer's software.

The following method is done with the Preview app.

But generally you will find this under the "Layout" section of the print dialogue. (See red arrow below)

If you are not seeing this much info in the print dialogue, you may need to click "show details" in the bottom left corner. (See red arrow below)

Awesome!

Yeah inside iPhoto/Photos, contact sheet works. If you wanted larger (two per page) you could select 5" X 7" or 4" X 6". Even making a custom would allow you to be very specific.

My method is if you were to open the desired photos into the Preview app from your Finder. This would require you to export the photos from iPhoto though.

All the best! 🙂