Go on You Tube and type Flower Stitch Foot Tutoral in the Search Box. Singer, SewOnLine and a couple others show you how to use it. You can use a single or double needle and you can use other design stitches with it, just write down what you did, the size of the flower and the stitch and needle you used with it. Keep the samples and notes with your foot. I think you will be happy that you have the foot once you view the tutorials.
I saw the flower foot attachment and thought that the ad was so cool that I bought one. I don't remember where I ordered it from, but they are all the same. I spent the next couple of days going over the book trying to figure out what was wrong, or why my flowers looked so wonky or bunch when I finished. Maybe there is someone out there who can make it work, but for me, it was a waste of money. It now resides in the back of my office desk drawer so I don't have to look at it and be frustrated anymore.
I remember at least one post about the circular foot. See the first link
I will look for a flower foot