There are many websites that provide guides and tutorials on iOS 10, the new operating system that powers Apple's devices which is soon to be released. However, in order to find the best iOS 10 guide that is easy to follow and understand, you will have to put in some effort to find the right websites.
Although there would normally be hundreds of websites each carrying all sorts of tutorials on iOS 10 or even any of its previous versions, it would only be a few that would have reliable information, the rest could simply mislead you. So, its best to avoid wasting time and referring directly to websites that you can trust for the information that they share.
The right website for you to refer to for iOS 10 guides, tutorials and upgrade information would be the one that someone with a good deal of experience in Apple's devices could recommend you to. You can visit technology forums and refer to sub sections that deal in iOS releases, you will have experts there advising you what course of action to take. There are also websites like iosmanuals which carry important resources and information on iOS 10 which you can go through. Make sure you bookmark resources that you come across online when looking for an iOS 10 guide as websites are updated regularly. This would enable you to check back again later for latest information.