How do I start using Apple Intelligence?

You must have an iPhone 15 Pro, iPhone 15 Pro Max, iPhone 16, iPhone 16 Plus, iPhone 16 Pro or an iPhone 16 Pro Max. If you have one of these then make sure your on the highest update, after that go to settings click: Siri and Apple intelligence then proceed to click join wait list. Within 10 minutes (least) to 2 weeks (at most) you should have Apple intelligence

How to get Apple Intelligence - Apple Support

Get started with Apple Intelligence on Mac - Apple Support