If you are a Parallels Desktop 12 user, the update to Parallels Desktop 12 was released yesterday. Please read this knowledge base article here to get a full walk-through. However, if you want to update an existing Windows 10 VM to the Creators Update build, you should get the latest update to Parallels Desktop first. Just ensure you’ve updated your Apple software first. If you have Windows 7 or 8.1 installed on a Mac, you can take advantage of the free upgrade offer and get Windows 10.
Apple now supports Windows 10 in Boot Camp.