You can either wait for your phone to remind you with a pop-up alert that iOS 14 is available or you can force a manual update. (Before you update, it’s always a good idea to back up your data.)
Navigate to Settings > General > Software Update and select Download and Install. If your iPhone has a passcode, you’ll be prompted to enter it. Agree to Apple’s terms and then…wait. You’ll see Update Requested on the screen, which means Apple has added you to its download queue.
Once it begins downloading, you’ll see a time estimate bar up top; how long you’ll wait depends on how many people are trying to upgrade. Your phone will then need to reboot, which could also take a few minutes.
If there’s not enough room on your iOS device, you’ll get a message asking to temporarily remove apps. Hit Continue and the apps will be restored when the installation is finished. If you have trust issues, hit Cancel and remove apps manually before returning to the update.
If you need your phone during the day, there’s also the option to Install Tonight, which will do exactly that—install iOS 14 while you sleep, provided your device is charging.
You can also turn on automatic updates. Go to Settings > General > Software Update > Automatic Updates. Your iOS device will then automatically update to the latest version of iOS overnight when it’s plugged in and connected to Wi-Fi.