Make sure your iPhone or iPad is updated to the latest iOS or iPadOS
Turn on Bluetooth
Turn on Location Services
Turn on Find My
Pull the AirTag battery tab to activate it
Hold the AirTag near your iPhone or iPad
Tap Connect when the setup screen appears
Choose a name for the AirTag
Register the AirTag to your Apple ID
Tap Continue and finish setup
Place the AirTag on or in the item you want to track