Congrats on your recent purchase of Dresden Plates.
If you want to applique them onto the muslin by hand, you need to cut your muslin squares an inch or so bigger than you want your finished block to be. Then fold the muslin in fourths and press. Lay your plate onto the muslin square using your pressing creases as a centering guideline. Pin, pin, pin!!! I use tiny applique pins, but you can use regular straight pins. Use a thin needle and silk thread to match. Turn about an 1/8" under on the outside of the plate and stitch down.
For the center, decide how big you want your circle to be-it has to be larger than the hole in your Dresden Plates. Next cut templates out of freezer paper the size you determine your circle to be. Then iron the shiny side of the freezer paper onto the fabric you purchased for the centers. Cut around each circle, about 1/8" bigger than the circle. When you have your center cut, leave the freezer paper in place and press the seam allowance onto the circle, using the edge of the freezer paper as your guide. Center on your Dresden Plate and stitch down by hand.
Here are a few websites that may help you too. Also check your local library for quilting books. I hope this helps you some.
http://www.hgtv.com/crafting/sizzling-dresden-plate/
http://www.quilterbydesign.com/lesso.../dresdens.html
http://www.mccallsquilting.com/qb/pattern_703/
http://www.quilt.com/FAQS/AppliqueFAQ.html