All you need to do is head on over to your iPhone or iPad’s Settings > General > Software Update and you should see the update there ready to be downloaded and installed. If you have automatic updates enabled, it should eventually download itself and be ready for installation whenever you’re free, but if you can’t wait, then you can always try and pull it manually.
Some of the changes that users can look forward to is a redesigned Safari that lets users choose if they want to relocate the URL bar, tab groups, a customizable start page, and more. iOS 15 will also improve on the notification system with larger photos and details, and there is also a new Focus mode designed to help keep you focused by letting you choose and limit notifications, and more.
While visually there doesn’t appear to be any major design changes, the update is quite a hefty one weighing in over 2GB, so make sure your phone is connected to a power outlet and WiFi before you download and install it.