The satin stitch is done with your zig zag stitch. I use the #20 foot on my Bernina. You need an opened toed foot so you can see what your're doing. You would set your necessary stitch width so you catch the outside edge of the applique and then a generous portion of the applique. The length of the stitch is set to a very short length. You need to practice inside and outside curves and "v" areas, like the "v" you would see in a heart pattern.

I forgot to mention that I use Sulky water soluble for stabilizer (underneath the quilt fabric). You can do as mentioned above and use a tear-away as well. It's not always necessary, but I think you'd find that a stabilizer will help you to get some nice secure stitches.

Machine Applique - Satin Stitch - Quilting Tutorial from ConnectingThreads.com
Applique - Fused Edge Prep - Quilting Tutorial from ConnectingThreads.com

Check out the links and also look at Youtube tutorials for doing satin stitch.