Hmmm...while looking at my Elna SU sewing Machine I will try to help.

Put spool of thread on spindle to the right.

Pull thread across top to the left and put in the back thread loop.

Pull thread forward and down thru thread loop at front left.

Bring thread down to left of upper thread tension (dial with numbers) and around the bottom and upward.

Place thread on the tread take up lever (lever that moves up and down at top front edge of machine).

Bring thread down thru thread guides, on down and to the needle.

Thread needle from the front to the back.

Put bobbin in the bobbin case with holes on top and thread coming off bobbin to the right.

Hold bobbin in place with finger to keep from unwinding and pull thread downward until you hear a tiny click. Close bobbin area.

Hold needle thread and use wheel on far right to move needle down and back up bringing bobbin thread up thru the hole and on top of machine.

You are ready to sew.

Here is a website that has a threading diagram and also sells manuals. Colleen

Here is a link that might be useful: Sew USA