Connect the iPad to Wi-Fi
Plug the iPad into power
Open Settings
Tap General
Tap Software Update
Wait for the iPad to check for updates
Tap Download and Install if an update is available
Enter your passcode if prompted
Agree to the terms if prompted
Wait for the download to finish
Tap Install Now if prompted
Keep the iPad connected to power and Wi-Fi during the update
Wait for the iPad to restart and complete the update