http://www.singerco.com/admin-suppor.../double-letter
Toward the bottom of the page on the right hand side after the red numbers you can order a manual. It is a model 15 made December 20, 1946. I have one and love it.
Is your needle in correctly? The flat side of the needle goes to the left (not back of machine) and it threads from inside out or right to left. Hope this helps:)