newbie here!

I have a vintage singer machine, I believe it is a 15-91. I bought it from someone in my neighborhood, but unfortunately they did not have a manual for it; I've searched the internet all over for a tutorial on how to thread it, but to no avail. I see that someone has recently posted about the same machine, so I figured someone in this forum would know how to thread it and get it sewing.

if anyone could help I'd be forever grateful!