Hi,
A few pictures would help. I am guessing your machine is like
https://www.worthpoint.com/worthoped...l-850-48980230 and if so, threading should be similar to
http://www.sewusa.com/Threading_Diag...ng_diagram.htm
Hopefully you can find a manual at the site bkay referred you to. I checked
http://www.sewusa.com/Sewing_Machine...g_Machines.htm and #36 is fairly close as it has lever type knobs as shown
http://www.sewusa.com/Deluxe%20Zig%2.../Deluxe36d.gif
If it is like the picture the for Deluxe 36, does your machine have similar markings? There were a few different ways of making buttonholes. If yours has the same markings for the buttonhole, you might be able to apply page 12 (11 of manual) of
http://www.singerco.com/uploads/down...-old-kzb-x.pdf for instructions on how to make the buttonhole.
I can't enlarge the worthpoint image to make sure which knobs are which..... guessing the left one on the the arm is for the buttonhole, the one on the right is for the width of the zigzag, the top dial on the pillar is for the stitch length and the knob on the bottom of the pillar is probably for reverse (just guessing).
Hope this helps. I'm hoping the link bkay gave you has your machine manual.
Janey - Neat people never make the exciting discoveries I do.