Actually, there are multiple ways to update iOS to 10.3. I will show one of the methods for you to reach this aim. Just follow below steps.
If a message says that an update is available, you could then click "Install Now" button to start to update your iPhone iOS software. Also, you could manually check whether there is an iPhone iOS update or not on your iPhone. The below steps would show you how to update iPhone software wirelessly:
Before you update iPhone software via WiFi connection, you need to make sure your iPhone has enough storage and battery to support the iPhone update.
Connect your iPhone to a WiFi network.
Tap "Settings > General > Software Update" successively.
Tap "Download and Install" option when your iPhone has detects an update available. If a message asks to temporarily remove apps because iOS needs more space for the update, tap Continue or Cancel. Later, iOS will reinstall apps that it removed.
Then iPhone would start to download and install iOS update immediately. You only need to wait for the update complete.
Answers & Comments
Actually, there are multiple ways to update iOS to 10.3. I will show one of the methods for you to reach this aim. Just follow below steps.
If a message says that an update is available, you could then click "Install Now" button to start to update your iPhone iOS software. Also, you could manually check whether there is an iPhone iOS update or not on your iPhone. The below steps would show you how to update iPhone software wirelessly: