I have machine similar to this one. The stitches are formed by changing the dial on the top of the machine and the uppermost dial on the face of the machine.
I can give you specifics later when I get home for work. I haven't used this machine in a while so I don't have the stitches memorized.
By the way, these machines sew well. I got mine in 1981 or 1982 and it is still going strong.
Margaret