How do I extend my apple care

Sorry, but what you provided is not accurate. AppleCare+ plans must be purchased within 60 days of purchase of an iPhone. If a valid AppleCare+ was not purchased in that time frame, it is not possible to add it. So, what we need to know is if the OP actually has an AppleCare+ plan or they are asking about extending the standard one year Apple Care plan. They cannot extend the standard AppleCare plan if they have owned their phone longer than 60 days.

If they have an AppleCare+ plan this is the link you should have provided if they want to extend it --> Extend your AppleCare+ coverage - Apple Support

Again, this ONLY applies if they purchased an AppleCare+ Plan at the time of purchase OR within 60 days of purchase of their iPhone. If they didn't buy a valid AppleCare+ Plan within the first 60 days, they cannot add one, nor extend the standard AppleCare which comes standard with all new iPhone purchases.

I wrote a user tip about AppleCare+, which includes a lot of information about these plans --> Demystifying AppleCare Plus / AppleCare P… - Apple Community

If you're still within a year of activation, you can buy an AppleCare Protection Plan from Apple Online Store or a Retail Store.

You can also buy an AppleCare+, but if you activated it more than 60 days ago you'll have to take the device to an Apple Store to be inspected in order to get it.

https://www.apple.com/support/products/

Thanks for the correction and precise information lobsterghost1.

You're welcome Rafael.