Some Singer 15s thread differently than the clones, you can't always use their instructions. Here is a generic manual for the clones that would probably be more useful to you than a Singer manual:
{
http://www.ismacs.net/singer_sewing_...ion-manual.pdf }
The clones needles go in
FLAT TO THE RIGHT and thread
LEFT TO RIGHT.
When you put the filled bobbin in the case and thread it, the bobbin should
ROTATE CLOCKWISE as you pull on the thread.
Joe