Where is the tension disk for the Hobbylock 603A Sewing Machines Parts and Sales in Los Angeles

I inherited a Hobbylock 603A from my mother. Though I have read the manual carefully I am not getting a consistent tension on my practice fabric. I think the problem is that I am not threading the tension disk properly but I’m not sure exactly where it is.

There are so many good, detailed pictures but not for this specific instruction. Can anyone help? With a picture if possible!

Thanks!