iOS notification for system updates appearing on the Settings app.
Here's a quick, simple, and no-nonsense way to update your Apple devices.
It is recommended to be on a stable Wi-Fi connection to update, and note that some updates are not available over a cellular connection.
Also, make sure that devices are on charge, or you have a charger handy in case it is requested.
From the iPhone
From the Apple Watch
There are many ways. The red dot on the Settings icon for the iPhone, iPad, and iPod Touch is the one most people are familiar with. WatchOS, TVOS, and MacOS will eventually notify you unless you carry out an manual update.
It depends. If it's a minor update (going from x.3 to x.4 say), then it can be over in a few minutes, but major updates (for example, going from version 15 to 16) can sometimes take an hour or more.
As well as getting new features and bug fixes, you also get security updates that help to keep your device safe from hackers and other bad guys.
Updates are quite safe. Yes, there might be bugs that cause you irritation, but serious issues that cause a device to be bricked or unusable are extremely rare.
Contact Apple support.