That's wonderful that you're starting off with the Dresden Plate! :)
Don't be afraid - what's the worst that can happen?
The heat-proof template is perfect for pressing the ends of the petal under in perfect arcs to prepare them for sewing onto your blocks.
If you use a little teeeeeeny bit of Elmer's Washable School Glue or Roxanne's Glue Baste-It along the raw edge after you've turned it under, you can glue the plate into place on the block and heat set it with your iron. The hardened glue will be far enough from the outer edge to be any bother to you while you're sewing the plate to the block and it won't come out until you wash it.
Soak it for a while in warm soapy water, give it an old-fashioned scrubbing between your thumbs under running water and the blocks will be clean and soft and ready to sew on the sashings or set into rows. :)