Here's a quick guide to two very simple operations, but which can put you in trouble if you're not very familiar with iPhones
Finding out which version of iOS is installed on your iPhone can trivially be motivated by curiosity, or it can be useful, for example, if you own an iPhone that's more than a few years old - which is likely if you bought it after a couple of years since its debut - and you want to figure out which version of iOS you're stuck with.
Upgrading your iPhone to the latest version of iOS involves performing steps that are within everyone's reach, but you should do it when you have some time. The steps, by themselves, are quick, but the download of the operating system is not, because, trivially, new systems usually weigh a lot - usually over a gigabyte - and therefore it can take more than an hour, even if you have a very fast Wi-Fi connection, for the iPhone to download the new operating system and install it. In other words, it's nothing complicated, but you'll need to be patient and have a good internet connection - not that of another smartphone, otherwise you might run out of "Giga" available.
How to find out the version of iOS
The steps you need to take to find out the version of iOS installed are simple and quick, to say the least. Simply open the iPhone's settings, scroll down to the General item, select it, and then tap Info: the number to the right of the Software Version item indicates just what version of iOS you have installed.
To get an idea, Apple started Monday the worldwide distribution of iOS 15 and for iPhones from the 6s model up to the newest ones. So anyone who owns an iPhone 6s or later with a version of iOS other than 15 can update their iPhone to the latest distribution. How? Let's see it right now.
How to update iPhone to the latest iOS version
To update iPhone to the latest iOS version, you need to open the General section within the settings and then tap on Software Update. From here you can start downloading the latest operating system and the phone itself will then provide instructions to proceed with the installation.
If instead the installed iOS version is the latest available then you will simply see iOS is updated, the same wording that appears if you are aware of a newer version of iOS than the one installed but the phone does not display it: it is highly likely, in this case, that the iPhone belongs to those that Apple does not update anymore because they are old.
Automatic Update
From the same Software Update submenu you can also set the automatic feature whereby the update is automatically installed overnight when the iPhone detects that a newer one is available.
You can decide whether to allow iOS to automatically download new updates (when you're connected to Wi-Fi) and/or to install them on its own overnight when the iPhone is charging: the best automation is achieved by selecting both items.