The utf-8 message just wants you to add the necessary meta tag to the <head> section of the page like:
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
You can't re-enter the wizard. If you want to make changes you can make them in Dreamweaver directly. What changes are you trying to make? If you are making major changes then you can always just delete the page and start over.