Question about sewing a bag together (attaching the bas Sewing Machines Parts and Sales in Los Angeles

This is my first non-pillowcase/non-hemming project, and I’m making a lunch bag. I’ve sewn all of the individual pieces, but now I’m confused on how to attach them. It says to stitch the bottom to the round part, but doesn’t mention how to do that. Is it by hand? Do I use a special machine technique?

Here are the directions for the step I’m on (#7).

Thanks!