How can I upgrade to iOS 16

Have a look at Apple's iOS 16 page How to update to iOS 16 or iPadOS 16 - Official Apple Support

Go first to the link at that page iOS 16 and iPadOS 16 are compatible with these devices to see if your current iPhone can be updated. You didn't state which model you have.

Go to Settings > General > Software Update > then down there you will see upgrade to iOS 16. Press on it, and then press on Download and Install.

Note: You will only see the ‘Upgrade to iOS 16’ option if your device is compatible

I have been having a serious issue with the wifi connections since updating to ios 16. I now have ios 16.1 on my iphone 12 pro max and it has been dropping connections like crazy. Even on my wife’s iphone 11 pro max it does the same thing while our kid’s phone connections are still good since they have androids for phones. I have been using my phone for more than a year and it never had this problem before. It all started when I updated my phone to the latest ios 16 software. I think I am switching if apple doesn’t fix this soon enough cause its really frustrating when you’re trying ro work on your phone and the signal drops every few seconds and comes back on again just to disconnect again. Very annoying and a very annoyed user.

Steve I