Use your template to bend your wire into your shape. This wire is pretty stiff and may require a little husbandly help to hold it in place while you bend. Once shaped, it holds though and you can resume working on your own.
Grab a needle and thread and tack your heart down to the canvas with a simple stitch–I’m not a sewer, so I’m not sure what the technical name would be for this stitch, but I think you get the idea here: up and down, as close to the wire as possible. As you can see, I tacked it down all the way around and then went back and added some “filler” stitches.