I purchased an iphone14 and need a user guide to help me navigate. How do I shut off my camera or move to a different screen?

Slide your finger up from the very bottom of the screen… you will then see the apps which are open, and can slide back and forth to find the one you need.. tap on an area where there is no app to get back to the Home Screen.

Here is a third party beginners guide which may be helpful:

https://m.youtube.com/watch?v=wo1aZWyZ2cI

alternatively a learning guide from apple:

iPhone 14 - Apple Support

hope that helps get you started trying out all the features your phone has for you to learn.